Graphical solutions of the problem of finding a ship's position at sea, by plotting and intersecting Sumner lines, lines of bearing, etc. being nowadays so general in our service, especially since the almost universal adoption of the Marcq St. Hilaire method, I am submitting a suggestion concerning what may be termed skeleton, or plotting, charts, which will, I believe, prove of great value and convenience to navigators, and of no great expense or trouble to the hydrographic office. For a plotting chart such as I have in Band there are three requisites:—
(a) It should be of sufficiently large scale to permit of accurate plotting and picking off.
(b) It should be sufficiently small in physical dimensions to permit of handy use on the restricted chart desks and in cramped chart rooms of modern fighting ships.
(c) It should be on paper sufficiently tough and durable to stand numerous erasures.
The following features are suggested, viz.:—
Projection.—Mercator.
Scale.—One inch equals 10' of arc in longitude.
Dimensions.—Between inner neat lines, 30 inches in width (5° of longitude) and a sufficient height to contain 5° of latitude stretched in conformity with the Mercator projection. Even 30 of longitude, 18 inches width, will suffice.
Delineation, Hydrography and Topography.—None needed.
Measuring Scale.—One of the interior meridians and one of the interior parallels to be subdivided into minutes of arc. For convenience the marginal lines might also be subdivided, but this is not strictly necessary; though the inner scales might become obliterated by frequent erasure.
Range of Chart.—From 0° to 60° in latitude, a set of 12 chart in all. Our ships rarely get in higher latitude than 60°. The charts are good in either north or south latitude.
I do not claim exclusive originality in this suggestion ; and 1 am aware that it may be said of such suggestion that on any ship of size the navigator or his midshipman assistant could easily construct such a chart in an hour or two, as needed; in fact I know that this has been done on occasion. But in these modern days of multiple and multifarious duties the navigator has little time except for sights and solutions, and his assistant is frequently so in name only, being primarily occupied with matters of gunnery training, fire-control, etc. And further, the accuracy of such improvised charts is open to question.
The general usefulness of such a plotting chart seems obvious; and its specific and particular handiness to the navigator who (at least in some of our ships) must, by rules of organization, spend a considerable portion of the precious forenoon in charge of the bridge, as the relief of the regular watch officer while he is away at drills and divisional duties, seems even more than obvious.
Later.—Acting on this suggestion the Hydrographic Office has prepared and is furnishing to ships a fine set of charts called "Position Plotting Sheet." Since writing the foregoing article I am informed by the editor that charts of this sort are used in the British service and have long been on sale in Great Britain and her colonies.