Experiments Made and Described by Max von Forster, First Lieutenant (Retired), Superintendent of the Gun- Cotton Factory of Wolff& Co., Walsrode, Germany.
Introduction.
We have, in continuation of previously published researches, experimented further with compressed gun-cotton as to its development of strength, using greater quantities of the explosive and noting the effect of confinement thereon.
We have endeavored to carry on the experiments under circumstances such as would present themselves in military practice. With reference to military use of compressed gun-cotton, we have considered the advisability of paraffining it, also of coating by dipping it into a solvent solution of acetic ether. Finally, we made numerous experiments with gun-cotton-charged shell as to their explosive effect, and facility of firing them from existing ordnance, considering especially the adaptability of granulated gun-cotton for charging the same.
In the recently published work of Lieutenant-General Brialmont, "La Fortification du Temps Present," Bruxelles, 1885, he refers particularly to the important effects of gun-cotton-charged shell, describing fully one charged with gun-cotton discs. This has encouraged us to hope that an account of our experiments may be of interest.
The experiments with gun-cotton shell made by us during several years past have been made entirely at our own expense and volition, with the exception of those made by the artillery authorities of a foreign power with steel gun-cotton shell six calibres in length, in the presence of the author.
A portion of the results of our experiments has been made generally known through the following-named imperial German patents granted to us in common with Mr. W. F. Wolff:
No. 22,418.—Method of exploding wet compressed gun-cotton under water. September 1, 1882.
No. 24,674.—Explosive projectile charged with pressed gun-cotton. January 14, 1883. Treating of a shell with unscrewing head, filled with gun-cotton in disc form, provided with a detonator which is independent of the fuse and is located more toward the base of the shell.
No. 26,014.—Method of wholly or partially coating compressed gun-cotton, nitrated wood and other cellulose by means of treating same with a solvent solution. March 9, 1883.
No. 33,867.—Method of filling hollow projectiles with compressed granulated explosive material. May 2, 1885.
Our experiments, so far as regards the nature of the objects destroyed, could only be carried on within the confines of a guncotton factory, yet it is believed they will afford a standard of comparison for objects of all kinds.
We can, however, call attention to the explosive effects of compressed gun-cotton in submarine work by recounting the destruction of sunken vessels and wrecks accomplished by us for the Imperial Admiralty, the Imperial Navigation Bureau at Wilhelmshaven, other public authorities, and for private persons.
In our experiments we have used exclusively the gun-cotton manufactured at the powder and gun-cotton factory of Messrs. Wolff & Co., Walsrode. This gun-cotton is in use in the German Army, has also been tested and accepted for the German Navy, a large quantity having been taken into store. It is supplied to many armies and navies in and beyond Europe. So it may be said to fulfill all the conditions of a first-class article of gun-cotton, and therefore we may consider the results attained with it as equivalent to those to be attained by any good gun-cotton. If not otherwise stated, the specific gravity of this gun-cotton is 1.1, and it has an average of 12.6 per cent, of nitrogen by weight, in the absolutely dry gun-cotton and included foreign matter.
It is known that wet gun-cotton can be detonated by means of a proportionate weight of dry gun-cotton, and we have so detonated it, whether special mention of the fact is made or not.
We detonated the dry gun-cotton by means of I gram fulminate-of-mercury detonators obtained from the Linden Primer Factory, Egestorf, Linden, near Hanover. These detonators retain their strength after a storage of five years, as we have so far found by experience.
Experiments with Regard to the Development of the Power of Compressed Gun-Cotton.
A.— Unconfined Dry and Wet Gun-Cotton Placed upon Leaden Cylinders and Detonated.
Experiments 1-4.—360 g. gun-cotton detonated upon a leaden cylinder 46 mm. diameter by too mm. high destroyed it; the dry gun-cotton half destroyed it, while the wet destroyed it entirely.
Experiment 5a.—6500 g. dry gun-cotton in discs 14 cm. diameter and a total height of 43 cm.
Experiment 5b.—6500 g. gun-cotton of same shape and dimensions and same dry weight, but with 25 per cent, of moisture.
In these two cases the gun-cotton was placed upon two blocks of rolled lead, each 15 cbcm. in volume, one above the other, and the two upon a perforated iron plate. The dry gun-cotton destroyed the upper leaden block, while the wet destroyed both.
Experiment 6.—A disc of dry gun-cotton 14 cm. diameter and 6 cm. high, weighing 920 g., provided with a detonator, was placed upon two leaden blocks as used in 5a, 5b, destroying them to about the same extent. It thus appears that an explosive charge of guncotton of 920 g. acts as powerfully on the object immediately under it as one of 6500 g., when the surfaces of the charges in contact with the object are equal. It may be that the detonator exercised an important influence in the development of the explosive force in this experiment; said influence will be more closely examined later.
In the continued experiments, the weight of the gun-cotton was so far reduced that the object upon which it was to develop its strength was not entirely destroyed; yet it was sufficiently great to produce craters in the leaden blocks with rims raised above the level of their upper surfaces, leaving the surface around the crater normal. To determine the comparative power developed, the rim of the crater was cut through down to the level of the upper surface of the block, and by filling the crater to that level with water from a glass tube graduated in cubic cm., the amount of lead displaced was determined. The greater the number of cubic cm. of lead displaced, the greater the development of strength by the gun-cotton. The leaden blocks used were of sufficient size—15 cm. cubes—to admit the use of a considerable weight of gun-cotton.
Gun-cotton cartridges 38 mm. diameter, 50 mm. high, and weighing 63 g.:
Experiment 7.—1 dry cartridge displaced 27 cbcm. lead.
Experiment 8.—1 wet cartridge detonated by dry one above it displaced 36 cbcm. lead.
Experiment 9.—8 dry cartridges, one above the other, displaced 33.5 cbcm. lead.
Gun-cotton cartridges 60 m. diameter, 50 mm. high, and of different weights:
Experiment 10.—1 dry cartridge, 1.1 sp. gr., weighing 153 g., displaced 60 cbcm. lead.
Experiment 11.—1 dry cartridge, 1.28 sp. gr., weighing 178 g., displaced 90 cbcm. lead.
Experiment 12.—1 dry cartridge, 1.28 sp. gr., weighing 175 g., displaced 90 cbcm. lead.
Experiment 13.—1 cartridge as in 11 and 12, but containing 18 per cent, moisture, and hollowed out to receive a dry priming charge of 32 g., 1.1 sp. gr. The weight (dry) of gun-cotton same as in 11 and 12, and the cubic space same as 10, 11 and 12. Amount of lead displaced 148 cbcm., thus displacing 2 ½ times as much lead as in 1 2/3, and if times as much as in 11 and 12.
Experiment 14.—Same as in 13, only the priming charge was 12.5 g.(?); so the whole cartridge had 12.5 g.(?) less gun-cotton in it; but the poorer result was not owing to this difference. Amount lead displaced 1 10 cbcm.
Experiment 15.—Cartridge as in 13 and 14; for priming charge there were used 8 discs, each 38 mm. diameter, placed one above the other, the detonator placed in the upper disc. Weight of each disc in priming charge 63 g. Amount of lead displaced 143 cbcm.
If, then, as has often been shown, the action of the last cartridge in long charges is reduced, in this case the eighth, it still fully served its purpose in developing the full power of the wet gun-cotton which it detonated.
Experiment 16.—3 cartridges, placed as before, each 60 mm. diameter, 50 mm. high, and of 1.1 sp. gr., weighing together 410 g., all dry, displaced lead 120 cbcm.
Experiment 17.—3 similar cartridges, but of 1.3 sp. gr., and weighing 488 g., displaced lead 200 cbcm.
Deductions.—Gun-cotton of a decidedly higher sp. gr. than 1.1 develops a materially greater power, and this increase is greater in proportion than the increase in the absolute weight of gun-cotton employed.
It is therefore generally advantageous for the development of power to employ gun-cotton of as high sp. gr. as possible, more especially in case the space for the reception of the charge is limited. However, the following experiments made with gun-cotton-charged shell, and with charges not in contact with the objects to be destroyed, show that under circumstances different from the preceding the advantage of gun-cotton of a higher sp.gr. does not manifest itself so directly.
Effect of Gun- Cotton upon Objects not in Contact with it, Hit Separated by an Air-Space.
In order to secure a starting-point for comparison in the following experiments, the preliminary experiment (1) was made:
(1). A disc of gun-cotton 60 mm. diameter, 1.2 sp. gr., and weighing 181 g., was placed upon a piece of wrought iron 30 mm. thick and detonated.
The effect was to make a bowl-shaped indentation in the iron of the diameter of the gun-cotton disc and of 8 mm. depth in the centre. In addition to this, the effect on the under side of the iron was considerable: it was nearly broken through.
(2). A disc of gun-cotton 60 mm. diameter, 1.3 sp. gr., and weighing 181 g., was placed 34 mm. above a similar piece of iron to that used in (1) and detonated. It made an impression 55 mm. diameter and of a depth from 3 to 4 mm.
(3). A disc of gun-cotton 60 mm. diameter, 1.1 sp. gr., weighing 156 g., was placed exactly as in (2) and detonated. It made an impression 55 mm. diameter and of a depth from 1 ½ to 2 mm. Moreover, in (2) and (3) the iron was separated lengthwise of the fibre, the crack running through to the under side.
The effect in general decreased, and in such way that the effect of (1) bore about the same relation to that of (2) which that of (2) bore to that of (3), and the differences of effect were considerable.
(4). A disc of gun-cotton, as in (2), of 1.3 sp. gr., was placed 100 mm. from the iron and detonated. Only traces of an impression were made.
(5). A disc of gun-cotton, as in (3), of 1.1 sp. gr., was placed 100 mm. from the iron and detonated. Traces of an impression were made, but fainter than in (4). The difference between effects in (4) and (5) was not very marked.
(6). Suspended in air 20 cm. from the trunk of a pine tree of 9 cm. diameter, and 35 cm. above the ground, was a charge of gun-cotton weighing 254 g. Upon the ground under the charge lay an oak plank 25 mm. thick. Upon detonation the bark was peeled off the pine tree, and a piece in the direction of its length was split from the plank.
(7). A charge of gun-cotton weighing 400 g. suspended in the same manner at 15 cm. from the trunk of the pine tree. Upon detonation the tree was cracked and another piece was split off the plank.
Deductions.—With an air-space between the gun-cotton and the object to be destroyed, the effect is very much reduced. With a greater air-space, the effect produced by gun-cotton of 1.1 sp. gr. Does not differ materially from that produced when the sp. gr. is 1.3.
B.—Explosive Experiments with Gun-Cotton Enclosed in Cast-iron Shell.
The gun-cotton was in the form of discs 139 mm. diameter and 50 mm. high, and of 1.1 sp. gr. The cavity in the shell was such as to receive these discs. The walls of the shell were 32 mm., the bottoms 60 mm., and the heads 120 mm. thick.
Two leaden blocks, 15 cbcm. in volume, resting upon a perforated iron plate, received the base of the shell. The upper block was always more or less destroyed. The effect could, however, be more accurately measured by the upsetting of the under block, and from the quantity of lead forced from its under side into the hole of the iron plate.
Experiment No. 1.—The shell was charged with 5200 g. dry guncotton, the detonator being placed at the greatest distance from the support—i. e., in the uppermost disc.
Experiment No. 2.—The shell was charged with gun-cotton containing 20 per cent, of moisture; the same weight of dry gun-cotton, however, as in No. 1. The upper disc was dry, and served as a priming charge to detonate the wet ones.
Experiment No. 3.—The charge of the shell consisted of guncotton containing 20 per cent, of moisture; the discs were hollowed out in line with the axis of the shell to a diameter of 50 mm. In the head of the shell was a disc of dry gun-cotton as a priming charge to detonate the wet.
In analogy with the explosive effects of unconfined gun-cotton, it appeared evident that there would be a specially powerful effect produced down through open central channel upon the support.
Experiment No. 4.—The shell was charged with gun-cotton containing 20 per cent, of moisture, though the bottom disc, weighing 930 g., was dry, and in it was placed the detonator.
The effect in 3—hollow-charged—was least; then came 1, next 2, and in 4 the effect was greatest, the disc which was detonated by the detonator, and which then detonated the other discs, being almost in contact with the object to be acted upon.
In experimenting, it has manifested itself that gun-cotton detonated by a fulminate-of-mercury detonator acts more powerfully than when detonated by other gun-cotton. In this manifestation the immediate distance to which the detonation of the detonator acts plays a role. As soon as this distance is exceeded we conclude that the gun-cotton is no longer detonated by the detonator, but by other gun-cotton which it has detonated.
To investigate more closely the influence of the detonator upon the violence of the detonation, the following experiment was made:
Experiment No. 5.—Three 15 cbcm. leaden blocks were hollowed out in the middle to a diameter of 23 mm.; a fourth block of the same size was only half bored through. These four blocks were placed one on top of the other, the half-bored one on the bottom, and were secured in place with iron straps. The cavity down through the centre of the leaden blocks, being 52.5 cm. in length, was provided with a charge of gun-cotton 45 mm. long, made up of several discs 22.5 mm. in diameter, the lower disc resting on the bottom. The upper disc was bored out to receive the detonator, which last was connected to a string fuse which passed through a hole in a lead plug fitted into the cavity in the upper lead block.
After detonation it was found that the leaden blocks were each divided into four quite regular pieces; upon placing the pieces together again, it was seen that the detonation had increased the central hollow very materially—to 230 mm. diameter in the upper part, and to 130 mm. diameter in the lower part. The proportional spheres would be about as 6: 1, so that we must conclude that the part of the charge detonated by the detonator produced six times the effect which was produced by that part of the charge detonated by guncotton.
We infer from these experiments that it may be possible, by changing the physical characteristics of gun-cotton, or by a different manner of producing detonation of the same, to secure a considerably higher development of power.
The detonation of the detonator caused the gases from the detonated gun-cotton to be powerfully effective; but these powerful gases, acting upon the elastic gun-cotton, lose some of their force, and are not capable of developing gases of the same power from the remaining gun-cotton. So far, it has not been possible for us to continue the experiments within leaden blocks, so that we might have employed gun-cotton of 1.3 sp. gr., or perhaps nitroglycerine, which is not elastic; yet the experiments with unconfined charges afford ample ground for comparison.
Nor have we had the opportunity to try the effect of shell filled with gun-cotton of 1.3 sp. gr. upon objects of sufficient resistance to endure and show full amount of destructive work done, and upon objects generally.
The difference in effect between wet and dry gun-cotton manifested itself very slightly in the experiments made with shell, yet it is possible that this difference may exist to a considerable extent in confined charges, and that it may have only manifested itself upon the object confining it. The base of the shell was amply thick for the purpose. This relation could not be proven, as cast iron is a material which does not offer sufficient resistance to permit the different effects to be fully developed.
It is improbable that confinement, on all sides of equal strength, would exert any influence upon the development of power in compressed gun-cotton.
If a disc of compressed gun-cotton is detonated upon an armor plate, or upon a sufficiently resisting piece of wrought iron, an exact impression of the face of the gun-cotton in contact will be left upon it, the dimensions of the impression being exactly those of the face of the gun-cotton in contact. The effect of the detonation only goes beyond this limit in that the immediately affected particles of the iron carry with them parts of those adjoining them. The gases generated by the detonation had, therefore, in the first instance, and as long as they exerted their maximum force, the exact form and occupied the same space as was occupied by the gun-cotton before detonation. How suddenly the power is exerted is shown by the following experiment: If between a gun-cotton disc and the iron plate there be placed a coin, after detonation the raised figures and letters thereof will be left impressed in the iron. If, instead of a coin, a leaf is used, then after detonation the whole frame or skeleton of the leaf is left raised upon the iron. The larger as well as the smaller ribs of the leaf protected the underlying parts of the iron, while the thinner parts between could not yield such protection, and under them the impression is deeper.
C.—Explosion of Shell upon Railway Rails.
We exploded a number of shell upon such objects as in actual practice it would often be desired to destroy; and for charging them we employed granulated gun-cotton.
15 cm. cast-iron shell 2 ½ calibres in length and of 2 litres charge capacity were filled with granulated gun-cotton. After charging, the shell were filled with melted paraffine, which will be more fully explained later. The dry as well as the wet grains of gun-cotton were coated by dipping in acetic ether. The explosive charges were:
Experiment No. 1.—Dry granulated gun-cotton 1200 g.
Experiment No. 2.—Gun-cotton with 25 per cent, moisture and 250 g. of dry.
Experiment No. 3.—Gun-cotton with 25 per cent, moisture and 150 g. of dry.
Experiment No. 4.—Gun-cotton with 25 per cent, moisture and 100 g. of dry.
Experiment No. 5.—Wholly paraffined gun-cotton and 300 g. dry, gelatinized.
Experiment No. 6.—Wholly paraffined gun-cotton and 200 g. dry, gelatinized.
Experiment No. 7.—Gun-cotton with 25 per cent, moisture and a priming charge 31 mm. diameter of 35 g.
Experiment No. 8.—Gun-cotton, dry, and a priming charge of 35 g.
Experiment No. 9.—Wholly paraffined gun-cotton, 150 g. dry guncotton, and a priming charge of 35 g.
Experiment No. 10.—Half a shell, divided lengthwise, filled with 1000 g. of gun-cotton in prisms (having a volume of 140 cbcm).
Experiment No. 11.—Two prisms as in lo, of 154 g. each, placed directly upon the base of a rail.
Experiment No. 12 —One such prism as in 11, laid upon a rail.
Each shell was provided with a priming charge 16 mm. diameter, weighing 9 g., for the reception of which a hole was left; in the priming charge was inserted the detonator of 1 g. fulminate of mercury
The shell were placed upon a platform composed of three rails, bottom side up, the heads brought as close together as possible.
All the shell exploded perfectly. The effect was nearly the same in all. The rails were generally cut through, and where this did not happen an equal development of power was manifested in some other way.
No. 10 produced no greater effect than the others, which tends to show that granulated gun-cotton acts as powerfully as do compressed gun-cotton discs.
In 11 the rail was smoothly cut twice, in 12 once, the effect in comparison with the preceding being greater; which goes to show that confinement does not increase, but does perceptibly reduce, the effect upon the immediately underlying object; which is explained by the fact that the 20 mm. thick wall of the shell separated the gun-cotton from the rail. We note that we are speaking of the immediate and direct effect upon the underlying object. There is a general effect, which is exerted upon more distant objects, which must not be confounded with the former, and in which such short distances as 20 mm. need not be considered. This difference furnishes the reason why only relatively reliable results can be obtained in experiments where the effect can only be produced on one side and upon an object in immediate contact, and why our experiments, one time with the gun-cotton in immediate contact with the object, another time confined within an interposing object, did not furnish regular and well-defined results.
If, moreover, no more effect is produced upon the support by nine discs of gun-cotton than by one (see Experiment A, 5a, 5b and 6), it does not follow that in the former there is not more power developed proportionally to weight of gun-cotton. At all events, even with exclusive reference to effect, wet gun-cotton is preferable to dry, as where it is desired to destroy such objects as walls, arches, armor plates, etc., with unconfined charges, care being taken to make contact surface between gun-cotton and object to be destroyed as great as possible.
Experiment No. 13.—A shell charged with granulated gun-cotton, wholly paraffined, provided with a priming charge 31 mm. diameter, weighing 65 g., placed in a cavity left therefore. Failed to detonate; portions of the charge burned.
Experiment No. 14.—A shell charged with granulated gun-cotton, wholly paraffined, provided with a priming charge 31 mm. diameter, weighing 100 g., was perfectly detonated.
In case a shell is charged with granulated gun-cotton and the charge is not cemented together, and to the shell, by means of melted paraffine, a much heavier and larger priming charge will be required to produce detonation.
Experiment No. 15.—A 21 cm. cast-iron shell charged with 4200 g. of dry granulated gun-cotton was placed upon a platform composed of a double layer of rails—five rails resting on their bottoms upon two wooden sills. On top of these were four rails, bottom up, in the interstices between the heads of the five bottom ones. The wooden sills were 1 m. apart.
The shell was covered to a depth of ½ m. with earth. The effect of the explosion was very marked. All the rails were cut through, most of them several times. In addition there was a hole made in the ground ½ m. deep. A bomb-proof cover would, in the light of this, be difficult of attainment.
D.—Effect of Gun- Cotton and Gun- Cotton- Charged Shell in the Ground.
Experiment No. 16.—A 15 cm. shell filled as before with granulated gun-cotton and buried 1 m. under ground produced in light earth, also in somewhat heavier earth, as loam and sand, a crater 60 cm. deep and 2 m. diameter.
Experiment No. 17.—A 15 cm. shell filled with 2100 g. ordinary cannon powder produced a crater 50 cm. deep, 2 m. long and 1 ½ m. wide.
Experiment No. 18.—A 15 cm. steel shell 6 calibres long, charged with 8.9 kg. granulated gun-cotton containing 25 per cent, of moisture, I kg. of dry grains, and a 35 g. priming charge, was so buried that its apex was 1 m. under ground, while its base was ¼ m. under. The crater produced was 1.3 m. deep and 4 m. diameter.
E. Experiments Comparing Effect Produced by Compressed Gun-Cotton Discs and Granulated Gun- Cotton.
The ground in which the experiments were conducted is a light sandy loam.
Experiment No. 19.—A tin case 3 calibres long, of 7 ½ l. capacity, filled with
3600 g. wet granulated gun-cotton
300 g. dry granulated gun-cotton
50 g. primary charge
5620 g. total weight of gun-cotton when dry
was buried so that one end was 1.2 m. under ground, the other only .9 m. The crater produced was 1.1 m. deep and 3.3 m diameter.
Experiment No. 20.—A charge of the same form as in 19, but consisting of wet gun-cotton discs of 8.3 kg. dry weight, and provided with a 50 g. priming charge, was buried as in 19. The crater produced was 1.3 m. deep and 4.1 m. diameter.
Experiment No. 21.—A tin case 6 calibres in length and of 15 1. capacity was filled with 11,150 g. of dry granulated gun-cotton (8 mm. cubes, gravimetric density; 75) and provided with a priming charge of 50 g., then buried so that one end was 1.2 m. and the other was .6 m. under ground. The crater produced was 1.58 m. deep and 4.45 m. diameter.
Experiment No. 22.—A charge composed of wet gun-cotton discs of 16.6 kg. dry weight, and provided with a priming charge of 50 g., was buried as in 21. The crater produced was 1.56 m. deep and 5.1 m. diameter.
A piece of wrought iron 3 cm. thick and 10 cm. square was in the first two experiments placed directly in contact with and under one corner of the tin cases, and in the second two it was placed parallel to the sides of the cases and 15 cm. below, and the interval filled in with earth. In 19, 21 and 22 the piece of wrought iron was compressed to about the same degree, but in 20 the compression was perceptibly greater. In 19 and 20, the iron being in immediate contact with the cases containing the explosive, the discs of compressed gun-cotton proved more powerful in their action than the granulated gun-cotton.
Experiment No. 23.—A piece of railway rail .5 m. long, 12 cm. high, with 10 cm. base, was put upon two pieces of pine each 10 cm. square, placed 25 cm. apart, the whole set 1.25 m. below the surface. Earth was filled in 25 cm. above the top of the rail. A tin case, as in 19, filled with 5620 g. dry granulated gun-cotton and provided with a 10 g. priming charge, was laid over the middle of the rail and at right angles to it; then the hole was filled in to the original level. After explosion the rail was cut in three parts across its entire profile; its base was pressed into the wood to a depth of 1 cm. The pieces of pine were not otherwise injured. The crater produced was 1.1 m. deep and 3.1 m. diameter. The pine pieces and fragments of rail were found 1.5 m. in the ground.
Experiment No. 24.—A charge of the same size as the tin case just used, composed of compressed gun-cotton discs of 8.3 kg. dry weight, and provided with a 50 g. priming charge, was located exactly as in 23.
The rail was cut to pieces almost in the same manner as before. There were only two pieces, however, out of which, towards the middle, a piece was broken from the upper surface in each. The base of the rail was not pressed into the pine supports, but they were cut in two straight across the middle. They evidently did not offer as much resistance as those used in 23. Beyond being cut in two they suffered no damage. The crater produced was 1.5 m. deep and 3.5 m. diameter, somewhat larger than in 23. The pieces of rail and wood were found 1.65 m. below the surface.
In both 23 and 24 the rail was cut, though placed 45 cm. below the charge. The bottoms of the craters produced were respectively 40 cm. and 80 cm. below the location of the charge. The pieces of rail and wood were forced into the ground to a depth of 90 cm., and at that depth the sandy earth was pulverized.
These experiments demonstrate that gun-cotton in either form produces powerful effects, not only in its immediate vicinity, but at appreciable distances.
It appears from these comparative experiments that, on the whole, the effect of equal volumes of granulated gun-cotton and compressed gun-cotton discs is about the same. The more than a third greater weight of gun-cotton in the compressed discs is scarcely realized in the general effect where a very considerable weight is employed and the object to be acted upon is not in immediate contact with the charge.
Whether, with regard to other objects, and under other circumstances, the advantage of greater weight of gun-cotton in the use of the compressed discs, instead of granulated gun-cotton, will make itself felt, remains unsettled; but from the preceding experiments we are constrained to think it will do so in a very slight degree.
We are further of the opinion that it is very doubtful whether by the employment of specifically heavier or higher explosives than compressed gun-cotton, as explosive gelatine, a mixture of nitrate of benzol and aniline with nitric acid, or lower oxides of nitrogen, etc., in shell, a greater effect would be produced.
In actual practice the shell will seldom be in contact with the object to be destroyed by their explosive action; they will generally be somewhat removed, as, in firing against masonry or armor, they will not be in contact therewith their whole length—only slightly or not at all; and it is just at short distances from the object that the difference between a high and a lower explosive is realized.
In cast-iron shell with thick walls, the effect of the higher explosive would, perhaps, not be otherwise realized than in the pulverization of these walls, a result not generally desired.
In order to obtain a satisfactory basis of comparison of the development of power, and its effect upon objects from the different explosives, they should be experimented with under conditions of their probable use in actual practice.
We copy a few paragraphs from the work of Lieutenant-General Brialmont, already referred to;
"Ordinary 21 cm. steel shells charged with 14J kg. of powder, fired from the Krupp rifled 21 cm. mortar at 45° elevation, forced themselves from 2 m. to 2.6 m. into the sandy earth of the firing ground at Meppen and produced elliptic craters 1.2 m. to 1.4 m. deep, 3.2 m. to 4.8 m. long, 3.2 m. to 4.0 m. wide. Fired at 28° and 60° elevation, less effect is produced.
"A steel torpedo shell 6 calibres in length, charged with 36 kg. of powder and fired at 35° elevation, produced a crater 1.0 m. to 2.2 m. deep, 3.2 m. to 5.0 m. long, 2.6 m. to 5.0 m. wide, which corresponds to a mean displacement of 7 cbm. of earth.
"In comparison with the foregoing, it appears that 21 cm. steel shell charged with gun-cotton force themselves 4 m. into the ground, there, lying nearly horizontally, produce craters 2.4 m. deep and 4.8 m. diameter, which corresponds to a mean displacement of 15 cbm. of earth.
"Arches made of the best concrete and 1.45 m. thick will be protected against the ordinary shell thrown from the 21 cm. rifled mortar by a covering of sandy earth 2.5 m. thick; against steel shell charged with 14 ½ kg. of powder by a similar covering 3 m. to 3.5 m. thick; and against torpedo shell charged with gun-cotton by a similar covering 5 m. thick.
"An earth-covering 5 m. thick will not be practicable, as fortifications would thus become too high, and the expense would be enormous. It is therefore suggested to leave off the earth-covering entirely and substitute a layer of granite or porphyry .8 m. thick, or a layer of Portland cement 1 m. to 1.2 m. thick.
"The experiments carried on in Silberberg in 1869 appear, however, to have demonstrated that perhaps this would not be sufficient protection even against the shell from the rifled mortar, when charged with powder only, as, since they made indentations ½ m. to 2/3 m. in depth, a second shell striking in the same spot would break through the arch."
Lieutenant-General Brialmont therefore believes that he cannot yet make a definite proposition; he suggests, however, that arches be made of the best concrete, 1 m. to 1.5 m. thick, and that they be covered with at least 3 m. of sandy earth. If this be not sufficient, then concrete must be substituted for part of the earth, or the depth of earth must be increased; or there must be added plate iron on the under side, which would appear to be the simplest and cheapest method.
The tendency appears to be toward the armored turret. We believe, however, that with large charges of gun-cotton even turrets can be effectively attacked.
Altogether, it appears that Lieutenant- General Brialmont regards the effect of gun-cotton shell, and their influence upon the future construction of fortifications, as of great importance.
Submarine Blasting with Compressed Gun-Cotton.
Blowing up the Tugboat Mathias Sinnes I, Sunk in the Rhine near the Railway Bridge of Rheinhausen, below Duisberg, by the Author and the Engineer Math. Rossenbeck.
The tug was a strong iron vessel built in the early days of such constructions, and was very solid in all its parts. Its stern was 200 m. from the railway bridge, which rests upon massive piers, and 100 m. from the right bank of the river, the hull pointing down stream and. lying about parallel with the current. At average high water there were 2 m. depth above the deck aft, and 6 m. forward. The wreck was to be removed, so as to obtain a certain depth of water over it, to realize which it was necessary to entirely remove the after and mid-ship portions. The current is so strong that it is impossible for a diver to descend without support against it.
A wooden barge was fitted with an iron shaft across its deck, on which, beyond the barge's side, an iron ladder was fitted to move freely in guides. When the ladder hung at the proper angle, it was held in place by a pulley, the lower part resting upon the wreck or some detached part of it, or upon the bottom, while the upper part projected at least 2 m. above the shaft. To the ladder was attached an iron shield 1 m. broad, which deflected the current. The ladder and its shield were raised and lowered by a pulley. The diver could reach the wreck by means of the ladder, and protected by the shield he could work, mostly with his left hand.
A second barge, of the largest kind, was decked over solidly and provided with a crane, by means of which and a chain the portions blown off were hoisted up.
Owing to the proximity of the railway bridge, and to avoid injuring it, great explosive charges could not be employed; nor would they have facilitated the work, but would have retarded it. No large charge, even one of 1000 kg. of the most powerful explosive, would have broken up the wreck in such a way as to make it possible to hoist up and get rid of the separate pieces. The explosion of such a charge would have produced a conglomeration of pieces of the wreck which, holding tenaciously together, could not have been hoisted up; nor would it have been possible then to finish the work with divers.
It became necessary, then, to blow off single parts by means of moderate charges, and hoist these up by means of barge and crane; so there were provided wooden boxes filled with 10 kg. of compressed gun-cotton, which were placed and exploded singly or in pairs.
The diver would descend by the ladder, place the charge advantageously, which, on account of the strong current, sometimes required hours to accomplish. He would come up, the ladder would be raised, the barge hauled out into the stream, and the charge exploded by electricity. The barge would be hauled back, the diver would descend and sling detached parts with the chain, an operation often consuming hours; then it would be attempted to raise them. Sometimes the attempt would be vain, as the apparently detached part was still connected with the wreck.
The plates were first raised, then the frames, the rudder, later the boilers, parts of the paddle-wheels, of the shaft, and of the engine. The shaft was of steel, 15 cm. diameter, and it was smoothly cut through several times with double charges of 20 kg. gun-cotton.
Powerful as is the effect of gun-cotton, yet there were over 100 explosions, consuming 1200 kg., necessary to remove the wreck to the desired depth. The after half was mostly raised; the other half was buried in the sand through violence of the explosions. The forward part, beyond the shaft, was very slightly worked upon, as it already lay under the desired depth of water.
It was again shown in this case that it is not possible to annihilate a vessel by explosion. Iron constructions cannot be made to disappear by explosion, unless they are raised and carried away afterward, or are forced under the bed of the stream thereby.
It is a different thing to sink a floating vessel. Explosive charges of 20 kg. gun-cotton, acting upon a suitable place on the outside of a ship and in immediate contact with it, will make a hole, but whether the damage will be great enough to sink her is doubtful. As to the effect when not in contact, we have observed that the explosion of 100 kg. of gun-cotton in deep water produces but a very slight effect on a floating object 100 m. distant; while the effect against rigid objects, as buildings, etc., of 100 kg. of gun-cotton exploded upon the ground will be felt at 500 to 800 m. distance.
Wrecks of wooden vessels are readily shattered to such an extent by explosion that the tide in ebbing and flooding, or other current, will carry away the pieces; and we have destroyed a number of such wrecks on the coast of the North Sea and in the mouths of the Jade and Weser. The charges were placed by divers against the sides of the vessel, where it was possible; otherwise they were lowered down upon it. They consisted of 100 kg. gun-cotton placed in rather long boxes. With small vessels two to three such charges well placed are sufficient, while with larger vessels a considerably greater number would be necessary.
Blasting in the Adlergrund.
In the Baltic, between Bornholm and Rugen, lies the Adlergrund, a shoal formed by bowlders resting on the bottom. The Royal Government had been deepening the shallowest places by hoisting up the bowlders by means of vessels provided with the necessary appliances. Divers descended and attached the chains or claws to the stones for raising them. In order to loosen the bowlders in their beds, and so facilitate the work, there were exploded numerous charges of 10 kg. gun-cotton in water from 4 to 6 m. deep. These explosions loosened each from two to four bowlders of about 2 cbm., forcing them well out of their beds.
Rock-Blasting in the Rhine to Deepen the Channel between Bingen and Coblenz.
In many places dangerous shoals exist in the Rhine, formed by rocks on the bottom; of these the Bingerloch is the most dangerous and best known. To remove these shoals the rocks are drilled from floats and other vessels to a depth proportional to the height of stone to be removed; the holes are filled with powder and tamped with sand, and the charges are exploded. After 10 to 20 explosions, vessels provided with diving apparatus are hauled over the exploded ground, and the debris is hoisted up and disposed of.
It is our opinion that if high explosives were employed in this work instead of powder, the operations of removing the debris, which now are the most expensive part of the work, would be simplified and cheapened. It would not be necessary to drill the blast-holes so deep, as the detonation of a high explosive in them would shatter the rock from the beginning to the end of the hole; while, using powder, the lower third of the hole and surrounding rock remains, as a rule, intact. High explosives are not employed, because, in case of failure to explode, which will happen now and again, the explosive would remain in the rock, and might be accidentally exploded by the workmen while at work clearing away the debris, resulting in loss of life and property.
Using nitroglycerine preparations, this might readily occur, as these explosives are not made insensitive to detonation by concussion, no matter how long left in water. Using gun-cotton, however, as has been described by the author in a previous publication, the charges can be arranged in cartridges so that after a certain time, say 24 hours, the charge will certainly be saturated, and so become insensitive to explosion by concussion or by the detonation of the detonator.
Though advantages will be realized by the use of gun-cotton in this sort of work, yet it is our opinion that with its use, or that of any other high explosive, drilling will still have to be resorted to. In deep water, which may be regarded as tamping, high explosives simply placed upon the bottom and detonated do not accomplish enough work in the way of breaking up the surrounding rock, hence the cost of explosive necessary to accomplish the desired work would be too great. The only case we think of where it would be advantageous to blast without drilling is where a large surface of rock is to be removed to a very slight depth, 10 to 15 cm. Here the increased expense for explosive material would be provided for in the saving by not drilling or removing the debris, and the saving of time.
Paraffining Gun-Cotton.
(1). Paraffining dry gun-cotton so that the paraffine permeates it entirely and occupies the place of water in wet gum-cotton. Wet gun-cotton in store loses its moisture in time, unless it is hermetically sealed, and has to be dampened again. To save this labor, it has often been suggested to substitute paraffined for wet gun-cotton, because paraffine does not evaporate.
This suggestion would be very useful if paraffine were calculated to take the place of water in the premises. This is in nowise the case. Paraffined gun-cotton is a substance which lies between the wet and the dry, and has lost the best characteristics of both.
The chief advantage of gun-cotton containing 25 per cent, of moisture is its incombustibility. This peculiarity takes from it, for purposes of handling, storing and transportation, the character of an explosive, and it is a great advantage to be able to store it in this condition, where very large quantities are concerned. This is peculiarly realized in case of fire in the magazine or its vicinity; if the lire should burn a considerable time, owing to the presence of other combustible materials, the gun-cotton in store might be spoiled danger can never arise.
So long as spontaneous decomposition cannot be considered absolutely impossible, will wet gun-cotton be preferable to all other explosives derived from nitrating organic substances, which are all inflammable, as with it there cannot occur spontaneous combustion. The characteristic of non-combustibility is what particularly recommends wet gun-cotton for military use, and makes it especially suitable for use in sea mines, as in this use circumstances combine to make it necessary to accumulate large quantities of explosive in one place. Such accumulation, in case of fire, is a great danger, as heat enough may be developed to produce an explosion.
Paraffined gun-cotton does not, however, possess the characteristic of non-combustibility, but is ignited by any and every little flame which may reach it, and, once ignited, it burns with the rapidity of dry gun-cotton. The rapidity with which fire spreads and develops in the explosive is the real measure of the danger which exists in a magazine filled with it.
For the further judgment of paraffined gun-cotton the following incident occurring at the factory in Walsrode may be cited: Pieces of gun-cotton only partially freed from acid were paraffined. After two years it was found to be decomposing; green spots and cheesy places made their appearance; the whole mass became soft and fluid. In other words, the same phenomena were observed as in the decomposition of dry gun-cotton of poor quality. In a similar grade of wet gun-cotton this decomposition has not been observed.
Not only does paraffining not prevent decomposition, but it really encourages it, everything considered. Paraffined gun-cotton is produced from the wet by drying it and then dipping in a paraffine bath of 65° C. and leaving it therein until the paraffine has permeated all parts. It takes from ½ to 1 hour, according to the size of the piece. If the bath is cooler, then a longer time is required.
This process is always injurious to the gun-cotton, for it is certain that at the temperature of 65° C. nitrous acid is evolved, as may be shown by the iodide-starch-paper test. The acid so evolved is shut in by the paraffine, and cannot evaporate, as can the acid which time develops in wet and dry gun-cotton not hermetically sealed.
Experience in the factory at Walsrode has amply demonstrated, verified by the iodide-starch-paper test, that a not very stable article of gun cotton which has opportunity to evaporate becomes more stable after a lapse of years. To be sure, the evolved acid will in part have been taken up by the chalk; the remainder will have disappeared, leaving the gun-cotton in a stabler condition. Slight traces of nitrous acid are developed in all gun-cotton, even at low temperatures. Digesting gun-cotton in warm, or sufficiently long in cold water, traces of nitrous acid will be noted in the water by the addition of sulphuric acid and iodide-zinc-starch solution. In this direction we made the following experiment: A sample of gun-cotton was washed until no trace of nitrous acid could be discovered in the wash-water. The sample was then placed in the drying cupboard for eight days and kept at the temperature of 30° C, again examined and traces of nitrous acid discovered. The same experiment repeated several times with the same sample invariably resulted in the same way. Wherefore we are constrained to believe that all gun-cotton contains nitrous acid.
But all potassium nitrate, as obtained in commerce and used for the manufacture of powder, contains nitrous acid. We applied to one of the most celebrated firms of chemical manufacturers for melted potassium nitrate free from it, and received as reply that they had not succeeded in producing such. Thereupon we attempted to produce it in our own laboratory by purifying with great care some that we had on hand. After purification it was placed in a tightly closing gas flask. Upon examination after several months had passed, the saltpeter was found to again contain nitrous acid.
Professor Himly, of Kiel, expressed himself several times to the author to the effect that "all nitro-com pounds are not stable, all organic substances decompose; for explosives only inorganic substances should be employed." True as this is in theory, practice does not warrant strict acceptance of the conclusion. It will, however, even in the case of gun-cotton, be well to take every precaution in its manufacture; and later, in preparing it for explosive charges, too great reliance must not be placed in its safety, as is often done to the neglect of proper care.
We note, further, that when nitrous acid is evolved and combines with the chalk, forming calcium nitrate, it will not be injurious to the gun-cotton so long as not more acid is evolved than the chalk can absorb. In spite of this, however, acid reaction is obtained with the liquid iodide-starch or iodide-zinc-starch test, for the calcium nitrate is dissolved by the water used in digesting the gun-cotton; if sulphuric acid is added, free nitrous acid is liberated, and indicated by the reaction. Gun-cotton may in fact be acid-free, and yet upon investigation give nitrous-acid reaction. From all of which we infer that it is a vain effort to attempt to produce gun-cotton free from nitrous acid. The gun-cotton just discussed is, however, to be distinguished from such as still contains perceptible quantities of free acid, even nitric acid. In the case of the latter, it is our opinion that instead of improving with time, it will deteriorate and decompose. We have not discovered evidence that pulped and moderately acid free gun-cotton will decompose by heat.
Returning to paraffined gun-cotton, we do not wish to be understood as having said that good gun-cotton would be decomposed to a dangerous degree by paraffining, but only that the process should be avoided when possible. Nor do we in general maintain that it is injurious to store good gun-cotton in hermetically sealed receptacles. We have, moreover, demonstrated that good gun-cotton so stored for years did not deteriorate, as proven by the iodide-starch test. We believe, however, that it will be better for all gun-cotton not to store it in hermetically sealed cases.
Turning to the physical characteristics of the paraffined gun-cotton, we find that its only similarity to the wet consists in being less sensitive to concussion than the dry, on account of which peculiarity paraffining has been mainly recommended; it is, however, more sensitive to concussion, and to being ignited thereby, than gun-cotton containing 15 per cent, of moisture. To demonstrate this we made the following experiment:
Firing with the Mauser infantry rifle at short range at gun-cotton discs 15 cm. diameter and 5 cm. thick, those containing 15 per cent, of water withstood three hits, while the paraffined ones were ignited at the third hit.
The shocks which gun-cotton will have to withstand in its use in sea mines are readily withstood by it in the dry state; therefore it is not necessary to resort to paraffining on that account. The charges for fish torpedoes form an exception, in that they are frequently exposed to the enemy's fire, and for this very reason the use of paraffined gun-cotton would be unadvisable.
Now that it is demonstrated that paraffined gun-cotton is not sufficiently non-susceptible to concussion, it must also be acknowledged that it has lost its capacity for being detonated by 1 g. of fulminate of mercury, and that it can only be detonated by means of a priming charge of dry gun-cotton. Again, as paraffine does not evaporate, any gun-cotton which has been permeated with it cannot afterwards be utilized for priming charges; while, to use wet guncotton as such, it is only necessary to dry it.
We therefore reiterate our opinion that paraffined gun-cotton is not a good form of that explosive.
In the work of Manuel Eissler, Mining Engineer, New York, 1885, "The Modern High Explosives," great injustice is done to guncotton. He states that experiments in England have demonstrated that it is so sensitive to concussion that in a harbor defense of sea mines the whole defense could be neutralized by one countermine, which would, upon explosion, explode in succession all the mines of the system. As a matter of fact, there is no navy in Europe which does not almost exclusively employ this explosive for charging its sea mines, except where the old powder mines are still used, and principally because of its non-sensitiveness to concussion, as well as on account of its other favorable characteristics. And, also, in his descriptions of the chemical analyses and characteristics of gun-cotton, Mr. Eissler shows that he does not appreciate the nature and character of the explosive.
(2). Paraffining dry gun-cotton so that the paraffine penetrates a few millimetres, and forms with the cotton penetrated an air and water-tight layer to protect the interior against moisture.—This practice suggests itself for the preparation of priming charges. The cavity for the detonator is closed by means of a piece of paper before dipping into the paraffine; after being thus treated these charges are protected against moisture for years. It is an improvement to coat the surface of the detonator cavity by applying acetic ether. Thus the priming charge is provided with a coating which will keep out moisture for a reasonable time after the paper cover has been broken through and the detonator inserted, even if placed in water. Sensitiveness to detonation is not decreased by this coat of dissolved gun-cotton, as it will detonate under water, and with water between the detonator and the surface of the cavity therefore.
For the priming charges of sea mines paraffining does not in any way recommend itself. However carefully it may be carried on, it is impossible to know whether the paraffine has penetrated just far enough or too far. There is always the possibility that the primer has been made unsusceptible to detonation by the detonator. Moreover, our observation goes to show that primers so prepared become cracked on the surface in time, thus opening themselves to the reception of moisture. A piece of gun-cotton is not a rigid object: it changes its form with change of temperature, and with change of moisture in the atmosphere.
These possibilities afford sufficient reason for the non-employment of paraffine in preparing primers for sea mines. It is better to protect them in store and in use by careful packing.
It should be further noted that air-dry primers will be detonated under all circumstances of season or weather by detonators containing 1 g. fulminate of mercury; so, if they be stored in dry and airy magazines, no fear need be entertained of failure to explode when good 1 g. detonators are used.
(3). Paraffining Wet Gun-Cotton.—Gun-cotton containing 25 per cent, of moisture may be penetrated several millimetres by paraffine, which, however, can go no farther, owing to the water within. The layer of paraffine remains perfect at medium temperatures, and affords a degree of protection against the evaporation of the moisture and against flaking. With considerable changes of temperature, as in freezing, numerous cracks form and the gun-cotton crumbles, thus neutralizing the two mentioned advantages. In the course of experiments made at the factory in Walsrode, it appeared that pieces of wet gun-cotton carefully paraffined might keep through one winter, but not through two, without cracking. So many cracks formed that there was no more obstacle to the evaporation of the water nor to crumbling than in the case of similar wet, unparaffined cotton. Not unimportant is the fact that the paraffine layer enlarges the pieces, so that in a given space less gun-cotton can be placed. In pieces of 140 cbcm. the enlargement amounts to 12 per cent. Thus there is added to the gun-cotton an appreciable weight of a very combustible substance, which, with the wood of the packing cases, increases the danger in case of fire. Small pieces are not at all suitable for paraffining. If the paraffine layer is thinner than about 2 mm., then it does not serve its purpose for even a short time. Again, it is to be noted that it is uncommonly difficult and expensive to paraffine a large quantity of wet gun-cotton so that all the pieces shall be well covered, and, finally, that the sensitiveness to detonation is reduced.
It was experimentally shown that pieces of wet, paraffined guncotton could not be detonated by a 150 g. primer when they were not in immediate contact, though only 10 mm. apart. In unconfined charges, therefore, partial explosions and total failures might readily be realized.
The result is, that in view of the increased expense and other disadvantages, we cannot recommend the use of wet paraffined guncotton.
Coating Gun-Cotton by Immersing it in a Solvent Solution, As Acetic Ether.
This treatment has given very satisfactory results during the three years it has been exhaustively experimented with. The coating maintains itself well; cracking and flaking occur in a very slight degree. A lot of wet, coated gun-cotton was packed in a tightly closing box and stored, and another lot in an open box, and placed under water. Though cracks were developed here and there on a few of the pieces, yet the form and solidity given by the press were maintained. The time during which wet gun-cotton will retain its moisture depends materially upon the manner of packing. The coating is not impenetrable, but it does protect, to a considerable extent, against the reception of moisture in dry, and against its loss in wet, gun-cotton. The principal advantage of coating is its characteristic of making the pieces nearly as firm and tough as wood. This advantage will be appreciated by all who have noticed the condition of well-compressed and packed gun-cotton after a long transportation. The coating is a protection against the formation of mould. If, however, the formation of mould is encouraged by the manner of packing and storing, and proceeds independently, as when it begins on the sides of the packing cases and gradually spreads over them and everything within, the pieces of gun-cotton will also be attacked, whether coated or not. If coated, however, the spores will not penetrate the coat, but remain on the exterior, and the mould may be washed or brushed off, and the structure and stability of the pieces will not be injured. It may be further noted that if wet gun-cotton upon which mould or other fungus is growing be placed in an airy place where it can dry, the growth of the fungus will be checked. It is also useful, when the cotton is in danger of injury from mould, caused by the climate or faulty packing and storage, to wet it with carbolic-acid solution.
Coating will recommend itself especially for gun-cotton to be used in fish torpedoes and sea mines, as it will have to withstand much transportation and handling and long storage. It will also be very useful in the case of cotton carried and used by troops in the field, and is absolutely necessary in the case of granulated gun-cotton for charging shells. In a shell so charged, upon being fired the charge will receive a violent shock, and be pulverized by the friction on the sides and base of the shell, and the powder may be ignited and so cause premature explosion. To avoid this, after charging the shell we pour in melted paraffine, which fills up the interstices, and upon cooling cements the grains to each other and the whole charge to the walls of the shell, making it a practically incompressible body, and prevents the upsetting of the charge or movement of any of its component parts. The coating on the individual grains prevents penetration of the melted paraffine, which is of great importance, as, if it penetrated, the sensitiveness to detonation would be so much reduced that priming charges would have to be increased to an extent that it would be difficult or impossible to insert them. All granulated gun-cotton is very much exposed to friction, and consequently to dusting, in handling, and only by coating does it become fit for transportation and war purposes. The sensitiveness to detonation is not at all reduced in coated gun-cotton, the dry remaining sensitive to the detonating action of the detonator, and the wet to the action of the dry. There is no reason why it should not be so, as in the process of coating there is no foreign matter added to the cotton. The acetic ether dissolves the cotton on the surface to the depth of the thickness of a sheet of paper, and this dissolved cotton upon the evaporation of the ether remains as a thin, closely fitting skin. This skin is composed of dry gun-cotton, and it has, therefore, been truly said that coating by dipping in acetic ether makes wet gun-cotton combustible.
In the meantime, the word ether may encourage the idea that after the formation of the coating there may remain in it inflammable vapors of ether. This is, however, in nowise the case; the ether of the solution evaporates rapidly, leaving behind the hard, dry skin alluded to.
The quantity of dry gun-cotton thus produced is very small indeed, amounting in a prism of 230 cbcm. to 1 g., and to less in one of 140 cbcm.—less than ½ per cent. A case containing 50 kg. wet, coated guncotton would also contain about ¼ kg. of dry, a quantity in itself no source of danger, and which, in comparison with the quantity of combustible material existing about all stores of wet gun-cotton, need not be taken into consideration. Gun-cotton is generally packed in wooden boxes pitched inside. The weight of wood for a 50 kg. box is 15 kg., the pitch ¼ kg. Ample combustible material is therefore on hand to produce sufficient heat in a magazine, in case of a serious fire, to evaporate all the water of the gun-cotton in it. The ½ per cent, of dry gun-cotton produced by coating would not change the relations, as it is not flying about in the form of dust to be ignited by any chance cause. As we have already intimated, we are of the opinion that keeping the gun-cotton wet precludes all danger in case of fire in a magazine, as it prevents a quick and violent development of it. We believe, however, that in all methods of packing so far practiced, a fire in the magazine would result in great injury to the gun-cotton, or, if the fire extinguishing apparatus were not very perfect and sufficient, in its total destruction. But in these premises coating would not influence the result. Coated gun-cotton retains the odor of the acetic ether for a long time. It disappears after a time, which indicates that all the ether has evaporated. A change in the gun-cotton or in the coating is not perceptible. We have also demonstrated that neither in the coating nor immediately under the same is there any acetic acid formed. If, however, in packing freshly coated gun-cotton there should be manifested traces of acetic acid, which might have been formed by the acetic-ether vapors mixing with atmospheric air, no harm would be done, as it can in nowise be injurious.
The practice of coating gun-cotton by dipping in acetic ether has been called "gelatinizing."
Gun-Cotton Shell.
It is admitted that the explosive effect of powder-charged shell against stone and iron arches, armored walls and turrets, is comparatively slight, and therefore great effort has been made to introduce shell charged with some high explosive. The most suitable explosive for the purpose appears to be compressed gun-cotton, for, while it is classed with the highest explosives, it is in a firm condition, easily handled, safe in transportation and storage, very slightly sensitive to concussion—not at all so in the wet slate—chemically stable during long periods of storage, and it has been known and used with good results by military men for the last twenty years.
Starting from this point, it has been our object to make compressed gun-cotton the means of giving to shell a more powerful explosive effect. We have succeeded in finding a form of charge for shell, after extensive firing and exploding experiments, which appears to satisfy all demands, in that it not only admits of the firing of the shell from ordinary rifled ordnance, cannons or mortars without bore or premature explosions, but insures their explosion at the object. This charge, gun-cotton as well as fuse, will withstand the blow of the propelling powder gases, and there is no danger that either part of it will explode prematurely on account of such blow. We have demonstrated this by the following experiments
(1). By firing a large number (over 200) of shell fully charged with gun-cotton from an 8.8 cm. cannon with 450 m. initial velocity. By firing from the 15 cm. rifled mortar with 200 m. initial velocity. By firing from a 15 cm. rifled cannon with 400 m, initial velocity. From the two last-mentioned pieces steel shells 6 calibres in length were also fired.
(2). By firing shell, out of which certain parts of the charge were left, against different targets, so that each part of the charge might be separately tested.
Besides the realized practical result that we fired these shells without any of them exploding in the bore, these experiments were made on the supposition that the shock of impact, at great final velocity, against a rigid object would be very much greater than that to be withstood in the bore by the action of the propelling powder gases against the shell. If the shell (from which the igniter has been removed, whose mission is to ignite the fuse on impact) withstands the former shock without exploding or even deforming any part of the explosive charge or fuse, it may with perfect safety be concluded that it will under all circumstances withstand the latter shock; and, also, that when the igniter is added, premature explosions are not to be anticipated, as it is the same which has been used in the fuses heretofore employed and found safe. In addition to the igniter there is a detonator in connection with the fuse, which is necessary to detonate the gun-cotton. This detonator, which plays the most important part in experiments with gun-cotton shells, was differently constructed from the usual sort, and located in the charge with regard to the greatest safety, and was thoroughly tested, as the experiments show. In addition to the detonator described in our patent, we made use of another which satisfied all demands. After a combination of wet and dry gun-cotton is accepted as suitable for shell charges, the remainder of the problem is one of fuses, difficult, to be sure, but which we believe we have entirely solved.
The following are the experiments which are to demonstrate the power of resistance against shocks of our gun-cotton charges for shell:
(a). We fired loaded shell against rigid targets at short range, the igniters, which we regarded as out of the sphere of the experiments, were left out; otherwise the shell were completely charged and fused. The igniters were omitted because percussion fuses were used, which, in connection with them, would have been ignited upon impact and so have detonated the detonator. The shell struck with great final velocity, about 420 m.
The targets were earth-banks, hard-wood structures, and wooden structures covered with wrought-iron plates. We found that the shell withstood the shock of impact well, not detonating when the igniter was removed. We increased the strength of the wrought-iron plates on the target as far as the tenacity of the shell permitted, and found that so long as the empty shells fired against it did not break up, the loaded shells would also remain intact. When the shell breaks upon impact, the parts of the charge in their forward movement come into direct contact with the iron, and the friction sets fire to the gun-cotton and detonates the fuse. There were numerous cases in which the shell broke, lodging fragments in the earth-bank behind the target 1 m. deep, without there occurring burning or detonation of any part of the charge.
(b). We fired against the same targets shell charged only with guncotton, or only with the fuse and detonator—the igniter left out.
The former we afterwards opened by placing a gun-cotton cartridge upon them and detonating it, and if the charge of the shell was not detonated thereby or burned, it was shown that the individual grains were not bruised, and that the charge, as a whole, had not been set forward or backward by the shock of discharge or impact. The latter we filled with peas and a wet priming charge, and after firing they were opened by boring out the bottom, when it was shown that the detonator had not been detonated.
From the 8.8 cm. gun we fired shell of the ordinary form, but of steel, under the same conditions as above described, obtaining very good results; but before publishing them we desire to carry them further.
While the experiments with partially charged shell demonstrated that our system of gun-cotton shell charges is safe in firing, those with completely charged shell showed that the fuse arrangement functioned very well, and that the charge was always completely detonated. Partial explosions of the charge did not appear when using granulated gun-cotton. The form of gun-cotton which we prefer for charging shells differs materially from the ordinary disc form heretofore used.
A shell charged with gun-cotton in disc form is minutely described in Lieutenant-General Brialmont's "La Fortification du Temps Present." The disc is not an advantageous form for gun-cotton to fill shell, as the projectile has to be made with movable head or base. We therefore also manufacture a granulated form, such that it can be put in the shell through the fuse-hole. Each grain has a sp. g. of over 1. The gravimetric density is .7. 700 g. (dry weight) fill a space of 1000 cbcm. The grains are rectangular, 8 to 12 mm. across, and either cubes or rectangles. They are gelatinized, thereby receiving a firm form and being protected against dusting. After the shell is charged with the grains, melted paraffine is poured in, which upon cooling cements them together and to the walls of the shell, forming a solid mass. For the larger shell, the principal part of the charge is composed of wet grains, to which are added about 200 g. dry grains, or enough to fill the shell. In using granulated nitrated cellulose for loading shells there will often occur partial explosions, burning or blowing away of part of the charge. Gun-cotton and other nitrated cellulose are more difficult to detonate than is generally supposed. We made the following experiments:
In a strong, tin-lined wooden box there was rammed wet uncompressed gun-cotton containing 30 per cent, of moisture, as hard as could be without the aid of mechanical appliances; the box had 1 cbm. capacity, and contained 50 pounds gun-cotton, dry weight. A piece of compressed gun-cotton weighing 500 g. was placed in the middle of this box and detonated, whereupon the box and its contents were torn to pieces and scattered in every direction, without causing even partial explosion or burning of the wet uncompressed cotton. A heap of similar cotton was laid on the ground, on top of which were placed 250 g. of compressed cotton and detonated. Again there was no explosion of the uncompressed cotton, though it could not escape the blow of the detonation.
Wet uncompressed gun-cotton is then to be considered as a non-explosive material. The transportation thereof in one of its lower orders, collodion-cotton, is permitted by the railways. There would be no danger to railway traffic if wet compressed gun-cotton were permitted to be transported under the same conditions as collodion cotton, as, in relation to the incidents and accidents of transportation, it may be considered as collodion-cotton, while for use as an explosive it is much more advantageous. To carry this idea into practice it would be necessary to lower the prescribed percentage of moisture to 25 per cent, for compressed gun-cotton, instead of 50 per cent., as in collodion-cotton, as the former will not absorb 50 per cent. Gun-cotton containing 25 per cent, of moisture is an article which, under all circumstances of possible railway accidents, could not be exploded.
In store, at the point of utilization, the wet gun-cotton will become dry if not moistened when needful, and so become sensitive to detonation by a detonator.
If the transportation of wet compressed gun-cotton were free, it would be possible to supply to small consumers a high explosive. A material service would thus be rendered to rural economy, where a high explosive would be of great use in road-building and clearing land, as in blasting rock and breaking up stumps and roots.
Dry uncompressed gun-cotton burns fiercely, may explode, but does not detonate; it can be used as gunpowder. The conditions of granulated gun-cotton are similar. It naturally does not offer great resistance to the blow of the priming charge; nor is great resistance to be expected from part of a granulated charge against the action of another part which has been detonated by the priming charge. Gun-cotton is itself difficult to detonate if not in large, heavy pieces; it yields as it receives the blow of the priming charge, and is only ignited or blown away. The finer the powder, the smaller and lighter the grains, the greater the inclination of the gun-cotton to burning or partial detonation, and therefore the priming charge must be large and the confinement great to realize complete detonation.
It is highly probable that it is not possible to detonate considerable quantities of most sorts of granulated nitrated cellulose in any practicable manner. With the granulated gun-cotton manufactured by us at Walsrode it is different. In the first place, the grains are not immoderately porous or light: they have the same composition as the larger masses of compressed gun-cotton. In the second place, the grains are not very small: 6 mm2 is the minimum size; we preferably make them of the maximum size, 1 mm. thick by 25 mm. long, as it is easier to manufacture the larger sort. In the third place, the paraffine which we pour into the shell after charging it forms with the grains a compact mass, which acts as a piece of compressed guncotton. Generally a 1 g. fulminate-of-mercury detonator was sufficient to detonate this mass when the grains were dry; if they were wet or paraffined, then a proportionally large priming charge had to be provided.
While in the case of a shell charged with wet granulated guncotton, the charge cemented in the shell with paraffine, a priming charge of 35 g. is ample, it would be insufficient in the case of a similar charge wholly paraffined. In the latter case there would be required so large a priming charge that it would be difficult or impossible to find room for it. If a 65 g. priming charge is not sufficient to produce detonation, then will one of 100 g. be insufficient, though in the course of the experiments it once proved sufficient. On the contrary, there will result partial detonations and burning. Moreover, paraffining enlarges the grains and so reduces the gravimetric density of gun-cotton.
These reasons, combined with the loss of chemical stability in paraffined grains, seem to make their employment altogether inadvisable.
In the case of the wet and dry granulated gun-cotton made by us and united in one mass by paraffine, there is no danger of partial detonations. In case of slight confinement even, as in a light tin case, the gun-cotton is readily detonated, as the experiments show, and as follows from the nature of the case.
It is not possible to avoid a loss in weight of the explosive when granulated instead of compressed gun-cotton is used, the sp. gr. being the same in each. Our experiments have shown, however, that the difference in destructive effect is not very marked. And in this connection it is in favor of the granulated gun-cotton that its shell, being in one piece, is stronger than the one made to be charged with compressed gun-cotton, which would have to be in two pieces. If not too great a demand is made on the strength of the shell, the sides of steel shell can be made thinner, and, in case of cast-iron ones, they may be lengthened, thus increasing the capacity for the explosive charge. Cast iron may still be considered as an acceptable material for shell in one piece. Thus may be secured a remarkably effective shell, yet a cheap one. Economy appears likely to become the only means of bringing gun-cotton shells to their greatest possible and, as it appears to us, necessary development, notwithstanding their always limited sphere of action. Granulated gun-cotton has the further advantage of furnishing a uniform explosive material for charging shell of all calibres and kinds. It is not necessary to enlarge upon the advantage this material has for the purpose over compressed gun-cotton, which would have to be provided of different sizes for different shell. The effort for uniformity in ammunition is well known, and shown to be necessary. Moreover, the use of this material will enable the whole stock on hand of cast-iron and steel shell to be converted into gun-cotton shell, thus not only securing for them a more powerful explosive effect, but also increasing greatly the number of fragments upon explosion, so that their effect must prove exceptionally great.
It is known that by casting a number of light bulkheads in the shell, and again by providing the shrapnel, the number of fragments realized from projectiles was greatly increased. The first method could only be applied to a limited class of shell, and so an increase of resulting fragments from shell generally is a great consideration. The second method has the disadvantage of creating a separate and peculiar kind of projectile, and it is admitted that shrapnel would be gladly dropped if an equivalent could be had in shell. The cast-iron shell charged with granulated gun-cotton is destined to realize great advantages in this direction, at least for use in fortification and siege artillery. It is hardly probable that gun-cotton shell will be introduced for field artillery.
The following experiments give an idea of the number of fragments to be realized from ordinary shell:
In a specially built compartment, walled in, well closed, lined with boards, and provided with an outlet for the gases, to moderate the effect of the most violent explosions, we exploded, and realized from an 8.8 cm. cast-iron shell weighing 7 kg. and charged with ordinary cannon powder 37 fragments, weighing altogether 6160 g. The same shell charged with granulated gun-cotton yielded 200 fragments each more than 10 g. heavy, and 600 fragments between 1 and 10 g. heavy. From an 8.8 cm. steel shell 6640 g. heavy and charged with granulated gun-cotton we realized 23 fragments of total weight 2260 g., and 127 fragments of total weight 2865 g., or 150 fragments of total weight 5125 g. From a cast-iron 15 cm. shell weighing 27 kg. and charged with ordinary cannon powder we realized 42 fragments. From the same shell charged with granulated gun-cotton we realized 376 fragments, each over 10 g. heavy, and 828 fragments, each from 1 to 10 g. heavy. A considerable part of a cast-iron shell is broken into minute fragments. In our examination we did not consider fragments of less than 1 g., though they deserve consideration, as most of them, through only the force derived from the explosion, were driven through boards 25 mm. thick; so that with them, in actual practice against troops, a considerable effect would be realized. Of fragments over 10 g.—which would receive velocity enough from the force of explosion to be effective at considerable distances—there were produced by the granulated gun-cotton charge nine times as many as by the powder charge; certainly an important result.
A peculiar characteristic of gun-cotton shell is, that unless provided with a retarded fuse they will explode upon impact, not an appreciable time after, as powder shell. In illustration of this we made the following experiments:
(a). Two targets 1 m. apart, and one behind the other, made of boards 40 mm. thick, were fired at with a gun-cotton shell, which went through the first, and exploded between the two.
(b). A target of boards 4 m. square was fired at with an 8.8 cm. cast-iron gun-cotton shell so that the shell struck the ground 2 m. in front of it. The shell exploded in front of the target, and the latter was penetrated by 135 fragments of the former.
(c). Two targets as in (a), but 2 m. apart, were fired at with an 8.8 cm. powder shell in such way that the centre of the target was struck. The shell went through both targets and exploded in an earth-bank beyond the second.
The powder shell was fused with the same percussion fuse as were the gun-cotton shells; the later explosion of the former cannot therefore be attributed to the fuse, as has heretofore been done, but must be due to the slower development of the powder gases as compared with the development of the gases from gun-cotton.
The characteristic of the gun-cotton shell, of exploding upon impact, must in many cases give it great advantage over the powder shell, as where objects are to be destroyed into which the shell cannot penetrate, as armor-plating or very strong masonry, struck at a small angle, from which the shell is deflected, and, if charged with powder, will be so late in exploding as to produce no effect; or again, in case of targets easily penetrated, when the powder shell will explode too late and beyond, as in trying to destroy ordnance stores and transportation trains.
By means of an interposed retardation in the fuse, through which detonation of the detonator is prevented upon impact, or by the use of a time fuse, the explosion of the gun-cotton shell may be regulated at pleasure. This retardation will be necessary in the bombarding of fortifications covered with earth, so that the latter may be penetrated before the shell explodes.
From the publications of the cast-steel works of F. Krupp in regard to their ordnance and firing experiments we copy the following paragraphs, as they appear to us to indicate where gun-cotton shell might be advantageously employed:
"Ordnance:—15cm. cannon 35 calibres in length.
" Projectiles:—
Kind of Projectile | Length of projectile | Total weight in kg. | Weight of shell-charge in kg. | |
Mm. | Calibre. | |||
Steel armor shell | 500 | 3.35 | 51 | 1.5 |
Ordinary cast-iron shell | 596 | 4 | 51 | 3.4 |
Ordinary cast-steel shell | 670 | 4.5 | 51 | 6.2 |
“The mortar is intended for a different class of attack and defense than is the cannon, and the projectile therefore should be constructed with regard to this difference of object. In general the walls of a mortar shell may be made much thinner than those of cannon shell, as the gas pressures upon them in the bore are about in the ratio 1:2. The mortar is intended for firing at great elevations. Its objects are (1) to destroy earthworks; (2) to reach troops behind cover; (3) to break down cover.
"(1). For destroying earthworks, shell are necessary which have great penetration before explosion, take a large charge, and are strong enough to compel the complete conversion of powder into gas.
"It is necessary to fire at great elevations, and to use retarded percussion fuses. Cast-iron shell are not well adapted for this purpose, as they must have thick walls, consequently taking smaller charges; and again, they do not offer sufficient resistance to the developed gases, explosion resulting before all the powder of the filling charge is burned. Much more effective in this direction are steel shell, as they are free from the indicated faults.
"In case of firing with reduced charges, the thickness of wall of the steel shell may be very much reduced. To attain the normal weight it is then permissible to lengthen the shell. In this way shell with capacity for large explosive charges are obtained, and we have the so-called torpedo shell.
"(2). To reach troops behind cover, shrapnel is employed.
"(3). To break down cover. While for the destruction of earthworks it is necessary to retard the action of the percussion fuse, to secure great penetration before explosion, for breaking down cover it is desirable to secure explosion upon impact; otherwise the shell will explode on the rise after impact, causing the loss of the explosive effect on the cover. As is known, it has not yet been possible to remedy this fault, nor is it probable that it will be done, as even with the most sensitive fuses a certain time elapses from the impact to the explosion of the shell; and from the nature of the case this must occur so. It is necessary to strive for the shortening of this interval as much as possible."
From these extracts we perceive that the armor shell has capacity for only a small charge; and in the case of the larger calibres of steel armor shell, fired with brown powder at an initial velocity of 500 m. or more, an ever so powerful shell charge would not materially increase the effect of the projectile, though it would do so to some extent, as it would at least clear the hole made by it.
The cast-iron and cast-steel shell have capacity for explosive charges sufficiently large to produce marked effects.
The steel torpedo shell is the most suitable form of projectile for the employment of gun-cotton charges.
For the destruction of earthworks the gun-cotton shell is of great importance, as it produces greater effect in earth than the powder shell. Retarding the action of the fuse is easily attained.
For breaking down cover the gun-cotton shell is indispensable, as only it realizes the desired object of explosion upon impact, which can never be attained with the powder shell, as the slowness of its explosion is inherent in the powder, and not due to the fuse, as our experiments have shown.
The cast-iron shell will be much improved if charged with guncotton, for the comparatively weak confinement it affords to the explosive charge, and the reduction of the same on account of the great thickness of the walls, are more than counterbalanced by the quicker and stronger action of gun-cotton over powder. A steel shell with thin walls is always, however, preferable.
In regard to shrapnel, we note that it is probable that they may be wholly superseded by cast-iron gun-cotton shell, as our experiments have demonstrated that the latter yield as considerable a number of fragments upon explosion as do the former. We repeat that the common 15 cm. cast-iron shell, charged with gun-cotton, yielded upon explosion 376 fragments, each over 10 g. heavy, and 823 fragments, each between 1 and 10 g. heavy.
We hope that Mr. F. Krupp, with the great facilities which his establishment offers, will soon enter upon experiments with gun-cotton shell, as it is evident that they are at least calculated to supply a remedy for many important deficiencies in the effect of projectiles. If with a changed trajectory they offer advantages in the premises, as we saw in mentioning their characteristic of explosion upon impact, then is the question of a more powerful explosive than powder for charging shell of the greatest importance, though not of equal importance for all shell, and it must be decided in the near future. Should Mr. Krupp take hold of these experiments, we are convinced that he would carry them to a satisfactory conclusion in the brilliant manner in which he has so far solved all ordnance problems. If we could be of any assistance in the premises, with our gun-cotton factory, and with our experience of years in explosives, we would always beat his disposition.
Interesting paragraphs in regard to the employment of gun-cotton shell are found in Major Schumann's work upon armored turrets, and indeed he says: "In England there has been adopted for coast fortifications plating upon the so-called .sandwich system, a combination of three to five plates of from 15 to 16 cm. thickness, with wood between.
"It may be expected that with the latest and materially improved steel shell, penetration enough will be secured so that, charged with a high explosive, upon explosion a very destructive effect will be realized upon the whole system. The penetration of the projectiles in the massive rolled iron armor of 40 to 60 cm. thickness will naturally be much less. In case the plates are soft, and so not easily cracked, there may be expected considerable effect from shell charged with high explosive, and which strike at or near the edges of the plates. The two latest improvements in shell support each other here.
"The Krupp shell, made of the very best material, forged with a hammer upon a former, receive by this method of manufacture a degree of strength and toughness which enables them to withstand breaking up better than solid shot. Withal, the tempering is so perfect that, for example, a shell fired from a 15 cm. gun 35 calibres long went through two 18 cm. plates and 25 cm. of wood between them, and the only effect upon it was to grind the point down 1 mm.
"The second improvement consists in utilizing high explosives for charging shell whose hardness and toughness admit their penetrating far enough into soft, vertical rolled iron plates to at least make effective a part of the high-explosive charge. Where, then, such armor can be struck with sufficient velocity to give these shells necessary penetration to utilize the force of their high-explosive charges, it will be necessary to find means to obviate this penetration.
"Armored targets to be directly attacked are (a) armored ships, (d) armored coast fortifications, and (c) armored turrets occurring in the general system of fortifications of a country.
"The object of the Schumann system of construction is to protect the armored turrets of a general system of fortification against the direct fire of armor shell out of long guns. This is done by building the turrets in the form of an umbrella, upon which the shells cannot strike perpendicularly. They will strike at an acute angle and be deflected without having produced any effect. The explosive effect of the shell would be the only thing to do damage, but it will not act in time, as the shell will explode too late, whether charged with powder or gun-cotton."
From these deductions of Major Schumann, it appears that he expects to realize material results from the use of high explosives as charges for armor shell, and we take occasion to note what follows in relation to the technical construction of the shell
If the shell which penetrates the armor is charged with gun-cotton, and this is detonated by the shock of the shell against the armor, and indeed without the action of the priming charge and detonator—we do not doubt that the dry priming charge is ignited or exploded; the question is, whether it detonates so as to detonate the wet gun-cotton—then it will detonate before the shell has exerted its full force, or too early. The development of the gases from the detonation of gun-cotton, as compared with their development from the explosion of powder, is instantaneous, as we have observed and reported, and this will be so whether detonation results from the action of the detonator or the shock of impact.
A fuse, even a retarded one, in a shell which strikes armor at right angles and penetrates it will not withstand the shock—it will break up—and therefore no result can be expected in delaying the explosion through retardation of the fuse. If dry gun-cotton, therefore, is detonated by the shock of impact, then the shell will explode too soon; if, however, it does not detonate, but simply ignites, it would be possible, by disposing of the detonator in the shell in such a way that it will not be detonated by the shock of the powder gases against it in the bore, and thus cause premature explosion, to retard the explosion of the shell; and, indeed, the action within the shell would probably be as follows: The detonator would be detonated by the burning dry gun-cotton, and would detonate such portion of the dry gun-cotton as remained unconsumed. It will not occur that there is no dry gun-cotton left for the detonator to act on. By way of experiment, the above conditions may be realized by taking a piece of dry gun-cotton which has a hole in it to receive the detonator, placing one therein, and setting fire to the gun-cotton at some point and observing the result. In a great number of these experiments which we personally made, the gun-cotton was always detonated by the ignition and burning thereof, supplemented by the detonation of the detonator.
We have demonstrated that the same thing occurs in shell. We believe, further, that, suitably constructed and properly located, the detonator will be more difficult to detonate by shock than it is to ignite dry gun-cotton by the same means. Again, it is not to be feared that after the dry gun-cotton has begun to burn, the shell will explode before the detonator is detonated. It is consequently quite possible that an armor shell charged with wet and dry gun-cotton, and provided with a detonator, but no fuse, may explode at the right time, that is, not too soon, as the development of the flame in the dry gun-cotton and carrying the same to the detonator consume a certain time. We are not aware that this has been demonstrated by experiment, but, on the other hand, it is quite evident that the circumstances will be much more favorable in the case of a shell which cannot, and should not, penetrate the armor. These shell will have the greatest possible explosive charge, and be provided with a fuse, naturally not a retarded one. Either the shell strikes the armor at an acute angle and is deflected, and it will upon striking, notwithstanding Major Schumann's opinion to the contrary, explode in a favorable position, being in contact with the armor its whole length, or it strikes at right angles, so that it breaks to pieces or is flattened. In either case it will explode at the right time to act with the whole explosive charge, as it will explode upon impact. We believe, therefore, that the Schumann armored constructions are not protected against the action of gun-cotton shell as they are against that of powder shell, and that gun-cotton shell will be of great service against armored constructions of all kinds.
The object of our experiments with gun-cotton shell has been to demonstrate that the ordinary shell may be converted into a guncotton shell very readily by means of an arrangement provided by us, and fired at great range from ordinary cannon, mortars and other ordnance, by means of the heretofore-employed powder; and to demonstrate the advantage thereof as compared with a proposed dynamite shell, to be propelled by compressed air from a peculiarly constructed gun, and as compared with many other proposed and some existing methods of throwing shell charged with high explosives; in all of which is necessary extraordinary apparatus, difficult of transportation, complicated in structure, and of great expense. We lay great stress upon the simplicity there is in the use of our guncotton shell, and feel in duty bound to express our opinion that, for throwing projectiles from guns, there should never be used anything but the compactest and cheapest power-developing agent, as gunpowder.
Our contrivances have reference only to the charging of heretofore ordinarily employed shell with gun-cotton. There is no change of material in any part, except in the explosive charge; even the weight of the gun-cotton-charged shell is the same as heretofore. These valuable results have been attained by us (1) through the manufacture of a new, peculiar, and suitable form of gun-cotton; (2) through a special arrangement in charging the shell, that is, filling them up afterward with melted paraffine; (3) through constructing a suitable fuse.
We are convinced that gun-cotton shell will perform much important service, even if they do not work wonders.
The effect of high explosives is overrated; for example, upon a small area of armor no high explosive will produce nearly so much effect as will be produced by a steel shell from a 30 or 40 cm. cannon. However, there are but few such guns, and it is not possible to move them about to any extent. In field and siege operations the increase of effect through increase in calibre of gun soon reaches its limit; it is doubtful if there is any way to secure increased effect except by increasing the explosive effect of shell. We believe that shell charged with high explosives are to play a great part in the future, even though they do not accomplish as much as is unreasonably expected from them. For the very reason that they will not work wonders, it is our further opinion that the high explosives must be so adapted to them that they may be employed in the ordnance as it exists.
We give these lines to the kindly-disposed reader with the assurance that, while we have often spoken pro domo, yet it has been our effort to carry on the experiments impartially, and to draw the conclusions from them in the same spirit.