When in the movie, Captain Horatio Hornblower made his landfall in the West Indies smack dab as he predicted, the crew let out a lusty cheer. Such histrionics, we smile, are just part of the Hollywood touch. Why if the crew of one of our Navy ships cheered whenever they sighted Nantucket or Koko Head on schedule, the captain would feel grossly insulted.
But Hollywood wasn’t kidding. It really was a feat to make a correct landfall in those days, and the captain really rated three cheers and a pat on the back. With the tools he had to work with, it was a real art. That’s the difference between navigating 175 years ago and today. Then it was an art; today it is a science.
Today we have the gyro compass, calibrated engine speeds, accurate chronometers, micro-vernier sextants, pre-computed tables, DR tracers, fathometers, loran, radar, and many other gadgets that make navigation just another job to do.
Captain Hornblower had only the bare essentials: the compass, the log, the glass, the lead, the quadrant, and a Time Piece (spelled in capitals) for taking a lunar observation. These were the tools. The navigator had to display skill and imagination and possess a philosophical outlook—all attributes of the artist.
Take the case of Captain Hornblower. His position mainly depended on two things: dead reckoning and latitude sights. His dead reckoning was based on about seven weeks at sea plus the time his ship was in the doldrums. It was the vector sum of all the courses steered and distances run, taking into account the variations in variation, the allowance for leeway which may be as high as four points, tide, current, bad steering, faulty log readings, and any number of things which added up to a very uncertain position.
The real help was the latitude sights. By shooting the sun or a star on the meridian, Captain Hornblower was able at least to apply it to the declination to get his latitude. It was the one element in navigation that Hornblower could place reliance on. It was the one feature on the chart which was reasonably accurate.
But even assuming he was on his correct latitude, he could be several degrees off in longitude—a day’s sailing or more. Obviously to make a perfect landfall, Captain Hornblower had a way to determine his longitude. Let us see how he did it.
We imagine that the first thing Hornblower did was to take a bearing on the sun at sunrise to get its amplitude (bearing north or south of the equator). Then checking into the tables of the Ephemeris, he got the true amplitude for his particular latitude and the declination of the sun. By subtracting the one from the other, he got the compass variation.
Now, since this was not Hornblower’s first trip to the West Indies, likely as not he knew from notes he had made before what the variation was in this area. Otherwise he possibly had a copy of the latest variation chart published by those well known nautical publishers, William Montaine and James Dodson. He therefore had a rough indication of his longitude. But this was no good for accuracy after more than a day or two of sailing.
Now if Hornblower had a chronometer, it would have been as easy as rolling off a log. But very few ships had chronometers at this time despite the fact that John Harrison had perfected a marine chronometer designed to determine longitude within 30 miles at the end of six weeks of voyage at sea. To tell time, all Hornblower had was the hour-glass and his watch.
One way to work out the longitude without a chronometer was to take the lunar distance. It was a complicated operation to say the least and it took three assistants. Here’s how one writer describes it:
“The sextant and quadrants being accurately adjusted, or the error of adjustments found, set their indices to the estimated distance and altitudes respectively. Now let the principal observer place his assistants in the most convenient situation possible, and desire them to be prepared when he is ready to observe the distance; then all are to begin to observe at the same time, and when the principal observer has brought the nearest limbs of the sun and moon, or the enlightened limb of the moon and a star into contact, he is to ask the other observers, if they are all ready; and being answered in the affirmative, then, as soon as he has obtained a perfect coincidence of the limbs of the objects, he is to make it known to his assistants, by calling out any particular word, as ‘Now,’ or ‘Done’ (the French call out ‘Top,’ which is to the same import). The person having the watch is immediately to write down first the second and then the minute of (the time) observation, the hour being previously marked; the principal observer is to read off the distance, using the magnifying glass, which he is to communicate to the time assistant, that it may be wrote after the time of observation.”1
The reason for the two extra assistants was to get the correction for parallax and refraction. Refraction is a fairly simple correction where there is only one body at progressive vertical altitudes above the horizon- When there are two, both of which are at different altitudes and at various angular distances apart, the correction gets somewhat complicated.
Now that Hornblower has taken his observation (he used the moon and the sun), he now must get his watch error. Remember —no chronometer.
Fortunately, being in the doldrums helped him out. At about nine o’clock, he took a sun sight and recorded the watch time. His plan was to find out what time it would be in the afternoon when the sun had the identical altitude. He figured that half way between the time of the morning sun sight and the time of the afternoon sight, the sun would cross the meridian overhead. All he had to do was to add the two times together and divide by two to get the local time.
Of course, Captain Hornblower was a foresighted person, so he took several sights in the forenoon to be matched up later in the afternoon. After all, the sky might be cloudy at an awkward moment if he depended only on one sight. Besides, he could average all the noon times to get his watch error. And with the ship sitting in one spot on the glassy sea, he had no distance run between sights to confuse the issue.
To make a long “Day’s Work” short, Captain Hornblower entered his ephemeris (Nautical Almanac) to obtain the moon’s distance from the sun for various times at the Meridian of Greenwich. He matched his corrected Lunar Distance with this table and extracted the Greenwich time. The difference between the Greenwich time and his local time (previously computed) gave him his longitude.
The fact that Captain Hornblower (in the movie) determined his position within limits of accuracy greater than the intrinsic accuracy of his instruments and tables proclaimed him an expert. The fact that he announced beforehand the precise time land would be sighted proclaimed his artistry.
Because of the difficulty in determining longitude, the majority of captains in Horn- blower’s day employed Traverse Tables and did their deep ocean sailing along latitudes. With the quadrant or sextant, the meridian sights became quite accurate. Navigators relied on them and it was standard practice to place the ship well east or west of the destination and to “home in” on the latitude. The serious disadvantage to this method was in wartime. Merchant ships would seek the latitudes of the British Channels long before it was necessary, and then sail along the parallel until they made land. Enemy raiders only had to sit and wait for them along latitude 49°-30' to capture many valuable prizes.
But the difficulty in determining longitude caused trouble in peacetime too—serious trouble.
There was the case of the Centurion 2whose captain, George Anson, having fought his way around the Horn, figured by DR that he was fully 10° west of the Cape. He hauled to the north and almost ran into land dead ahead. He had to come about and waste many vital days beating to westward again.
Vital days they were, as scurvy had broken out among the crew. Men were dying daily. It was absolutely essential for the ship to make port as soon as possible to get fresh vegetables to treat the sick.
When Anson finally rounded the Horn and headed north to the island of Juan Fernandez, he decided to take a gamble and head directly for the island rather than to a point well east and follow the latitude in. The latter course would have been safer— but also longer. In the end, the Centurion missed his landfall. Since Anson didn’t know whether he was east or west, he wasted still more vital days beating back and forth along the latitude of the island looking for it.
The Centurion lost about eighty men on this trip, many of whom might have been saved if Captain Anson could have determined his longitude with any degree of certainty.
It is amazing today to realize the reluctance with which the invention of the chronometer was accepted by the navigation world. It was a case of repeatedly having to show to make people believe. John Harrison invented an instrument about 1760 on his fourth try that should have revolutionized navigation within a decade. Here, finally, was an accurate method of determining longitude. Yet 30 years later, John Hamilton Moore, England’s foremost navigational authority, comments in his Practical Navigator, “that could they [watches] be depended upon in all situations, and all Temperatures of the Atmosphere, would doubtless ascertain the Longitude of Places. But. ...”
Lacking the chronometer, what did they have?
The compass. The first instrument of navigation. But in Hornblower’s time the accuracy of the compass varied so much that it was a matter of conjecture today how some navigators ever found the place for which they were headed. In the first place, the compasses themselves were usually in error. Dr. Gowin Knight ran tests on many of them and found that their lozenge-shaped needles were weak, unreliable, and easily susceptible to induced magnetism. He developed a more reliable compass that used the straight magnetic needle and this was gradually adopted by the British Navy. Undoubtedly, Captain Hornblower had one of these on his ship.
Besides the inaccuracy of the compass itself, there was variation. A great number of seamen neither understood nor cared about this phenomenon. Some honestly believed that variation was “built” into the directions on the charts and that it wasn’t necessary to correct for it. But there were others who fully appreciated this “mystery of nature” and philosophically considered it to.be “a secret that God has been pleased to reserve from the knowledge of mankind.” This being so, it was all the more reason for the mariner to be a “strict and careful observer of the variation in every part of the Globe he may happen to sail.”
Hornblower did not subscribe to the practice of the Dutch of having a movable compass card which could be reset over the needle for every change of 2%° in variation. He much preferred to apply his variation in his calculations. There was too much chance of error in making the delicate adjustment of the card. Besides, Hornblower had been noticing lately that the compass would vary as much as 8 degrees from no other cause than coming about and heading the ship in another direction. Surely, this deviation was caused by some other phenomena than the usual variation encountered at various places on the globe.
Next to the compass came the log, marked fifty feet per knot, and the thirty second glass. Only sometimes, the line was measured dry and shrunk to less than fifty feet when wet. Also sometimes, the glass was only 28 seconds instead of thirty seconds. Of course, there were some captains who preferred the shorter spacing between the knots to have the reckoning ahead of the actual position so that the ship did not come up on land unexpectedly. But not Hornblower. He was most meticulous in measuring his line. It had to measure exactly 50 2/3 feet when wet. He checked his glass regularly and insisted that it be kept in a dry warm place when not in use.
But he was the exception. With so many errors creeping in by way of leeway, currents, and sea, many navigators ignored the inaccuracies of the compass and the log and placed their reliance on the three LLL’s.
Latitude, Lead, and Look-Out. Sir John Norris, “a brave and well experienced admiral . . . used to say, the three LLL’s were the best guides in coming into the Channel.”3
First is Latitude. Navigators in Horn- blower’s day placed their main reliance on a good meridian sight when out of sight of land. But whenever the DR latitude differed from the observed latitude, there was always, considerable juggling to be done to determine whether the error lay in the course or in the distance—or in both.
Here is how one serious minded navigator put it:
“First, Consider whether you have made proper Allowances for Currents, Heave of the Sea, if the Course at the Helm has been attended to, if the log-line and Half-minute Glass be just, and the Log properly hove, or any sudden Squalls, or proper Allowances made for the Leeway, &c. which of these you conjecture your Error is in; make what allowances you think meet to your Difference of Latitude and Departure by Dead Reckoning, and see if that will reform your Latitude by Account, so as to make it agree with our Latitude by Observation; if it does, you have guessed right; (for you must always keep to the Latitude by Observation, it being the only thing to be depended on;) but if it will not agree with the observed Latitude, it is to be supposed that there are Mistakes in your conjecture, or some other Cause which produces the Error in the Reckoning, and stands in need of being corrected. In this Case, you are first to examine your log-line and Half-minute Glass, and if there be an Error in them, allow for it.”4
If still the Latitudes did not match, then it became a matter for the “considered judgement and experience of the navigator to divide the error in such proportion as he may think proper to allow.”
It was quite proper to list Latitude first among the three LLL’s. Before entering the English Channel, the first thing the prudent navigator did was to set his ship on an easterly heading between Latitude 49°-20' and 49°-30'. On this latitude he was able to enter the Chops of the Channel some 175 miles west of and slightly south of the Scilly Islands. There the navigator began to use the second of the three LLL’s; the Lead.
There he would strike sounding in about 95 fathoms.
As an added check on his latitude, in case the sky was overcast, the captain would then haul to the southward keeping the lead going each hour. If he found that the water deepened to 110, 115, or 120 fathoms in the space of 20-40 miles, then he would wear ship and stand to the north, back to his original latitude feeling fairly certain he knew where he was. (It is a peculiarity of the 100 fathom curve at this location that it ran north and south above latitude 49° N and East and West below this latitude. We wonder how many of the navigators today place any reliance on this phenomena?)
From now on the second and the third L’s, Lead and Look-Out, become increasingly important. The main thing was to pass south of the Scillies in 62 to 64 fathoms (fine white sand) at which time “you may be sure these soundings will carry you 8 or 9 leagues to the southward”—safe from the rocks.
Take the sad case of the Nancy Packet. The Captain (a contemporary of Hornblower) was running up Channel in a fair way south of Scilly. At midnight he took it in his head to haul to the northward until the Nancy Packet ran “stem-long” against the steep rocks of the Scillies, dashing herself to pieces and sinking at once. All souls perished.
We know of this from a transport which was following the Nancy Packet. The transport like a lost and foolish sheep almost followed the Nancy Packet to disaster. Fortunately the captain, although he neglected the first two of the LLL’s, did not overlook the third. He had a good lookout posted. The lookout saw no land but heard the noise of breakers. Whereupon the Captain dropped the hook and thought things over. The next morning the Captain saw the wreck of the Nancy, her masts just out of the water and thanked Providence for being kinder to him than he deserved.5
The whole point of the story was that had the Nancy Packet stayed on her Latitude and taken soundings, the Lead would have told the Captain that he was abreast of the Scillies. By keeping on to the eastward until daylight he would have shoaled in 55 fathoms and been able to haul to the northward and make the Lizard with safety.
Navigating up the English Channel in foul weather was tricky business. There were the rocks of the Scillies, one of the most treacherous group of pinnacles in the world, the Owers just east of the Isle of Wight, the Rip Raps and Goodwin Sands, the graveyard of more ships than anyone knows. To negotiate this passage in the usual winter weather required years of experience and an expert knowledge of soundings.
Fortunately, there were many fairly accurate sailing directions published during the 18th century. One, by William Nichelson published in 1792, gave the details of sailing up the channel under unfavorable conditions and makes interesting reading even today.
Nichelson recounts an experience of his which in addition to testifying to his expertness revealed something of the man and the artist.
“In the year 1748, I was in a Man of War coming up Channel from Plymouth, bound to the Downs, in the latter end of October, there were 70 or 80 sail of ships in company, all bound up Channel; we were about 5 p.m. between Dunnose and the west end of the Owers, rather nearest the Owers, and at this time nearly high water in the offing, the wind slew round from SE. to south and SbE. with some rain, and continued between SbE. and south all night, with drizzling rain, and began to snuffle and blow fresh, which obliged us to take in our small sails and single reef the topsails, all the ships in company tacked and stood to the westward, but us in the Man of War, who continued to stand to the eastward; my Captain made use of the following argument with me, who at that time was Master of the Man of War, says he, it is very strange that you will advise our standing to the eastward, when all the ships that were in company have tacked and stood to the westward; there must be many experienced men in so great a number of ships, who are apprehensive of the danger of the Owers, by their discontinuing to stand to the eastward with the wind to the southward as it now is; and though I have a very good opinion of your knowledge and experience in the Channel, yet I wish you not to be too positive in this matter, in standing to the eastward, which may be attended with serious or bad consequences, should we not be able to weather the Owers, and especially as we differ in opinion from all the ships that were in company, who are all tacked and stood to the westward, and are now out of sight.
“To which I replied, Sir, I am obliged to you for the caution you have given me, and reminding me of the danger of risque we may run, should we not be able to weather the Owers, and as to the ships that were in company, their tacking and standing to the westward does not give me any concern; I compare a fleet of ships to a flock of sheep, one goes through the hedge and all the rest will follow; I shall take no example from them contrary to my own sense, reason and experience, there is no danger in our standing on to the eastward, the ship goes quick through the water, makes but little leeway, we will keep the lead constantly going, and as long as we can keep in 22 or 21 fathoms water, we need fear no danger from the Owers, but if we should shoal the water to 20 fathoms or under, we will tack and stand to the westward. The Captain was satisfied with my reasoning, and we continued to stand on to the eastward, the wind nearly south, the ship lay up no better than ESE all night, we kept the lead constantly going, and had 23, 22, 21, 22, 23, 22, 22, 21, 21 and 22 fathoms water, and never had less than 21 or 22 fathoms; the ship sailed at the rate of 5 or 6 knots all night, the moon got up about 2 o’clock in the morning. At 4 A.M. saw Beachy Head bearing NbW, distance 4 leagues; at noon got into the Downs. I must here observe, the fleet of ships that were in company with us in coming up the Channel when we were off the west end of the Owers, did not get into the Downs till 30 hours after us. So much for not following the crowd, and making use of our own reason, and keeping the lead constantly going, which is the surest and best guide in navigating a ship where soundings can be had, or where there are soundings.”
This last was sage advice. This last is sage advice—even with the fantastic gadgets we have at our disposal.
Despite all the difficulties Hornblower and his contemporaries navigated under, things weren’t too bad and they were progressively getting better. It wasn’t half as bad as it used to be during early colonial days when many captains sailed to the New World with little knowledge of the rudiments of navigation.
Some of these captains made use of an unusual oblique chart which was distorted to place Cape Race, which is on the Southern tip of Newfoundland, at the same latitude as the Scilly Islands at the entrance of the English Channel, even though it was actually over 3 degrees or about 200 miles farther South. With this erroneous chart, the ship also had a compass whose needle was set a half point or about 5 degrees to the east of magnetic north. By using this chart and compass with the built-in error, the captain had no difficulty in laying his course from England to Newfoundland, he knew it was due West and he sailed his ship in that direction the whole way. Because of the compass error and the change in the variation of the compass as the ship sailed across the Atlantic, he would wind up well South of his latitude and actually make his landfall at Cape Race as planned, a distance of almost 2000 miles.
Hornblower, of course, didn’t approve of such short cuts. He quite preferred the most up to date East Indian or Admiralty Mercator charts, even though the longitude lines were sometimes drawn inaccurately and many positions of the shore did not check with his own observations.
But then they even had trouble finding the position on land in Hornblower’s time. For instance, two separate navigation books6 gave the position of St. Mary’s in the Scilly Islands as:
49°-57' N and 50°-6' N
6°-36' W and 6°-49' W
It isn’t the fact that a couple of navigators disagreed as to where to put the Island. It is the small detail that neither one was right and there was a maximum error of about 24 miles from the true position.
No wonder the Nancy Packet el cetera, el cetera, were shipwrecked!
The refinements in radar and loran do much to take the guesswork out of navigation today. In foggy weather ocean liners slice through the channel at 25 knots as the radar operator reports, “Lizard head, bearing 349° distance 23 miles.”
Compared to this scientific exactitude, the navigation of Hornblower’s time seems almost primitive. But that is not true.
The tools were primitive in comparison, but the men that used them successfully possessed a skill and artistry that seldom are equalled today. Instruments and methods are now designed to take the guesswork out of navigation—to remove as much of the human element as possible.
One hundred and seventy-five years ago, it was the guesswork—the human element that counted. It was the seaman’s eye that calculated the allowance for leeway, it was the seaman’s experience that carried the ship safely by Goodwin Sands in a fog.
As one writer wrote around 1790, a seaman “does not spring up like a Mushroom, it requires many years to make him a seaman; it is service at sea, and long experience, . . . with fatigue of body and mind.”
But even this is not enough. In the final analysis there existed in the minds of all great seamen a deep conviction “that our own utmost skill, caution, vigilance, and dexterity, are altogether insufficient of themselves to command success in our proceeding, or preserve us from the many dangers and difficulties we are exposed to, without God’s all powerful protection and assistance.”7
In the entire scope of navigation, this belief is the one and only heritage that has come down to us without change.
1. The Theory and Practice of Finding the Longitude, Andrew Mackay (1810).
2. John Harrison and his Timekeepers, Rupert T. Gould, RN (ret.) and A Voyage Round the World by George Anson, edited by Richard Walter (1748).
3. A Treatise on Practical Navigation and Seamanship, William Nichelson (1792).
4. The Practical Navigator, John Hamilton Moore (1791).
5. A Treatise on Practical Navigation and Seamanship, William Nichelson (1792).
6. One of these navigational authorities was John Hamilton Moore: Every naval officer studied Moore’s Practical Navigator in those days—even Lord Nelson whose personal copy is now on display at the National Maritime Museum at Greenwich. It was these very same errors in Moore’s book that gave our Nathaniel Bowditch his start. Bowditch was commissioned by an American publisher to revise Moore’s treatise. But Bowditch found so many errors he decided to write his own book. Today, his American Practical Navigator (Revised) is still the navigator’s Bible in the United States Navy.
7. A Treatise on Practical Navigation and Seamanship, William Nichelson (1792).
