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Captain Cook as a Hydrographer


CCSU Meeting 1983 - Lecture Number 2

It was in 1759 that Cook, then at the age of thirty, gained his first practical experience in surveying. He was serving as a master in H.M.S. Pembroke and was one of a number of Masters employed in sounding and buoying the very dangerous channels of the St. Lawrence River which made possible the attack on Quebec and the safe passage of the fleet in waters where the enemy had not dared to risk their vessels.

His natural gift for this type of work was quickly recognised by Admiral Saunders who arranged to have him appointed in September of that year to H.M.S. Northumberland. Cook spent the winter studying the theoretical side of surveying and attained considerable knowledge of the subject. In the Spring of the following year, the Northumberland operated in the St Lawrence, and Cook continued his surveys of the Quebec Basin.

During the period October 1760 to August 1762, he charted parts of the Nova Scotia and Newfoundland coasts. After St. Johns was recaptured from the French in September 1762 his surveys of harbours are said to have "arrested the notice of Captain Graves, Governor of Newfoundland". Cook then returned to England in the Northumberland and was briefly unemployed.

In 1763 he was appointed as Master-in-command of the Schooner Grenville, the Governor of Newfoundland's despatch vessel. This was designated as a Survey Vessel and Cook was ordered to make surveys of the coasts of Labrador and Newfoundland. He spent four summers in surveying, and returned to London each winter to draw and compile his charts. He obtained the Admiralty's permission to print and publish four of these charts with sailing directions,

Cook's early training and experience was in close association with military engineers, especially Holland and Des Barres, during the operations of the Louisburg, Quebec and Newfoundland campaigns, and it was they who taught him how to construct his marine surveys on a network of shore triangulation. These methods which he used for charting Newfoundland and where he worked from measured bases on land, are quite different to his charting of the Pacific where it was necessary to employ other techniques which I will mention later.

For the Newfoundland survey he took with him a very good outfit of instruments including a brass telescopic octant made by John Bird. He also took a theodolite, drawing instruments and some small station flags. The inclusion of the theodolite indicated that the survey would not be by a running traverse from the ship, but by the observation of angles from shore stations. The title of the chart of the coast from Point Ferolle to Cape Auguille, commences with the words "an exact trigonometrical survey". It is very unfortunate that there are no traces of his plan of triangulation or the positions of his main stations on the original documents.

Cook described in his journal his operations during the 1764 season and it gives us a good indication of his methods. He commenced his surveying in the north on July 14th. He went into the Bay Sacre, measured a base line and fixed some flags on the different islands. He completed the survey of the bay and the islands in six days. He then carried out a similar survey of Pistolet Bay, to the west, and by the end of the month he had completed the survey as far as Cape Norman, the latitude of which was fixed by meridional observation.

The survey continued south-west to Point Ferolle using the same methods to the end of the summer. Harbours were carefully planned from a measured base line, fixing points by triangulation with the theodolite, and then running for the next harbour, sketching in the coastline, taking soundings, and frequently fixing the ship's position by quadrant angles or compass bearings on the shore stations determined by the theodolite observations. The latitude of prominent coastal features was observed by quadrant, and variation with the azimuth compass. The distances between such points, computed from their latitude and true bearing from one another, provided more extended base-lines.

The survey was completed in 1767 and, with the Admiralty's permission, his charts were published. These surveys were not superseded until, over a hundred years later, a new Admiralty survey was made. A Captain Bayfield who spent thirty years on survey work in the Gulf and the St. Lawrence River, remarked in his journal that "the chart of Red Island and adjacent coast, etc ... by Captain Cook is extremely correct. If ... the nature of the coast, cliffs etc., had been shown, the survey would have been perfect".

Perhaps we should now move on and examine Cook's Pacific surveys.

His instructions for each of the three voyages were practically identical in wording. On the discovery of land or islands, he was directed to explore "as great an extent of it as you can, carefully observing the true situation thereof both in latitude and longitude, the variation of the needle, bearings of headlands, height, direction and course of the tides and currents, depths and soundings of the sea, shoals, rocks etc., and also surveying and making charts and taking views of such bays, harbours and different parts of the coast, and making such notations thereon as may be useful either to navigation or commerce". (This is only a brief extract from Cook's instructions.)

Cook was well provided with some of the best instruments available for astronomical observation and surveying. They were made by the leading mathematical instrument makers of the day - Bird, Nairn, Dollond, Ramsden and Adams. There are records of the instruments which were carried on the Pacific voyages and these show that apart from the usual instruments (quadrants, sextants and compasses) a theodolite, Gunters chain and a plane table were included, indicating that Cook was equipped for trigonometrical surveys similar to these he carried out in Newfoundland. However, he had few opportunities for this method of survey in the Pacific and it was only used for the charting of a few harbours, and some short sections of adjacent coast.

The Endeavour and Resolution journals give very little detail of Cook's method of survey, and unfortunately there are practically no rough drafts among the surviving charts to provide firm evidence of their construction. Because Cook seldom had the time or the opportunity to go ashore to fix positions by regular triangulation, the framework of his surveys was, of necessity, the astronomically determined positions of the ship and of coastal features. The scale of his charts had to be derived from the computed distances between fixes, to which the ship's dead reckoning, from compass and log, was adjusted.

Little time was wasted during the voyages. On the 1st voyage, he charted the coasts of New Zealand - some 2400 miles, in six months, and a further 2000 miles of the east coast of Australia in four months. Despite the speed with which the surveys were completed, their accuracy was quite remarkable. If we compare his chart of New Zealand with the modern chart, it shows that the errors in Longitude rarely exceed half a degree, except in the north of the South Island.

It is obvious however that Cook was dissatisfied with the methods he was forced to adopt, and he would have preferred to have spent much more time in each area, to have landed more frequently, and thus to have produced charts with more detail and greater accuracy. Whilst making a sketch survey of an island in the New Hebrides in August 1774, he noted in his journal "The word survey is not to be understood here in its literal sense". Another entry referred to his chart of New Zealand in these terms: "The coast as it is laid down from Cape Saunders to Cape South, and even to Cape West is no doubt in many places very erroneous as we hardly ever were able to keep near the shore and were sometimes blown off altogether".

Considerable importance was attached to the astronomical observations on the Pacific voyages and this is why some of the best astronomers of the day were detailed to accompany Cook. In the Endeavour on the First Voyage he had Green from the observatory at Greenwich; William Wales and William Bayly were on the Second Voyage in Resolution, and for the last voyage, Bayly sailed in Discovery whilst Cook did his own observations in the Resolution assisted by Lieut. King.

Perhaps we might briefly consider the fixing of position by observation.

Latitude, produced by Meridian altitudes of the sun - taken with either a quadrant or sextant, were fairly reliable. For instance, the latitude of the observatory at Point Venus in Tahiti, differed by only 3" from the correct figure (about 100 yards) .

The uncertain factor was longitude. With some accurate means of keeping the time, it would not have been too much of a problem, but Cook did not have a chronometer with him in the Endeavour although John Harrison's 4th chronometer had passed its tests at sea in 1764. He therefore had to determine longitude by the "Lunar Distance" method .

Briefly, this involved observing the moon's angular distance from the sun, or from a suitable star; at the moment of observation, Greenwich time was obtained from tables which predicted the moon's motion and position in relation to other celestial bodies; then comparison with the local time gave the observer his longitude.

Using the tables which Maskelyne published, it would have taken between three and four hours to perform the necessary calculations. The improved tables in the Nautical Almanac, which was first published in 1767, gave the angular distances between the moon and each of a number of suitably placed bright stars and the sun, for every 3rd hour of Greenwich time for the whole year and reduced the computing time to perhaps under half-an-hour.

In the Resolution, Cook carried a famous chronometer; that was made to Harrison's design by Larcum Kendall. Despite having this valuable aid with him, Cook continued taking lunars on every possible occasion. Comparisons were then made with the longitude obtained by the chronometer, and frequently found only small differences. Other opportunities were also used to fix longitude by observing eclipses of the sun and moon, the transit of fixed stars, and other predictable phenomena.

As I said earlier, Cook did occasionally manage to get ashore to make plans of a few harbours by triangulation, but other harbour plans were made only from sketches. On one occasion Cook wrote "I have made no accurate survey of this bay, the time it would have required discouraged me from attempting it".

In circumnavigating New Zealand, Cook plotted his track by fixing the ship's position from his courses and from intersecting bearings on landmarks, adjusted from time to time the astronomical observations. Analysing the records of the 1778 voyage, William Wales tells us that Cook "determined the ship's position from time to time by means of a series of triangles which he carried on all round the island, and which formed a continued connection of the situations of the ship with remarkable objects inland and the principal points of the coast; and he made no further use of the log than to connect those points of the track which the ship was in, when he took his angles and bearings".

It appears from the journals that Cook and his master spent a good deal of time at the masthead, and there are many references to his ascent of coastal hills "to take a view of the country", to set the different points, or to take the necessary bearings. Cook tried using an azimuth compass for this purpose but found it unsatisfactory. Perhaps this is why on his last voyage he took with him two small Hadley's sextants of 5" radius, by Ramsden.

There were only three major mistakes in Cook's charting which he did not himself detect. The delineation of the Banks Peninsula (in the South Island of New Zealand) as an island; of Stewart Island as a peninsula, and his failure to determine the insular character of Tasmania. This illustrates the explorer's difficulty in distinguishing between a strait and a gulf or deep bay when he is unable or reluctant to keep close inshore.

A great deal of the plotting was delegated by Cook to his officers, as was some of the surveying. The journal of his last voyage contains this passage "I had several young men amongst my sea-officers who, under my direction, could be usefully employed in constructing charts, in taking views of the coasts... and in drawing plans of the bays and harbours in which we should anchor".

There are some references to this practice in the journals. In June 1770 he "sent some of the young gentlemen to take a plan of the harbour". In December 1774 Lieutenants Pickersgill and Clerke charted Christmas Sound to the west of Cape Horn, and in January 1777 Henry Roberts (masters mate) charted Adventure Bay in Tasmania. Cook told the Admiralty that the charts of the Second Voyage were "constructed partly from my own observations and partly from Mr. Gilberts my master. The views are all by Mr. Hodges".

After Cook's death, William Bligh, who was sailing master of the Resolution, claimed that he was responsible for the survey of the Friendly Islands and for all the surveys carried out after Cook's death, including those of the Sandwich Islands .

There are many differences between the charts of Cook's Newfoundland period and those drawn by him and his officers after 1768. The latter are commonly graduated in both latitude and longitude whereas the Newfoundland charts are graduated only in latitude. For the Pacific voyages, Cook carried his longitude from Greenwich, and not from London, unlike Wallis and his other predecessors, and the Endeavour was the first ship employed on discovery in which the prime meridian of Greenwich was adopted - no doubt because of his use of the nautical almanac tables.

Cook anticipated modern practice in naming his discoveries by using, whenever possible, the place names used by the natives. This sometimes proved difficult but he made good use of a Tahitian who was on board the Endeavour, as an interpreter and also of a vocabulary of eight dialects which had been compiled by William Anderson, the surgeon in Resolution. In a few cases he did use English place names.

Many of Cook's original charts of the voyages have unfortunately been lost, but some are preserved in the British Museum, some in the Public Records Office, and a journal complete with charts of New Zealand, New Holland and the South Sea is in the Mitchell Library in Sydney.

With his death in February 1779, the world lost someone who has been described as "the greatest seaman-explorer the world has known. A man who aimed at perfection in all that he undertook, and who established certainties where hitherto there had been doubts".

In closing I can do no better than remind you of some of the words inscribed on Cook's monument at Chalfont-St-Giles in Buckinghamshire

"To the memory of Captain James Cook, the ablest and most renowned navigator this or any other country has produced".

K.J. Snowdon
National Maritime Museum

Originally published in Cook's Log, page 290, volume 7, number 4 (1984).

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Jim, I will contact you to discuss the answer to your enquiry as it is too long to describe here.
By Cliff Thornton on 1/14/2015 9:45:09 AM Like:0 DisLike:0
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I am interested in knowing the details of how Cook charted a coastline from a running traverse. In particular, how many men would be used and what were their specific jobs? Presumably, he ran a straight course at constant speed and took multiple sextant (?) angles on land formations and then fixed distances via trigonometry. However, this suggests he had one to take bearings, one to keep time and one to make marks upon the nascent chart. In short, I'd like to learn precisely how this was done.
By Jim Thoen on 1/7/2015 12:35:19 AM Like:1 DisLike:0
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The best sources for original material on Cook's voyages are "The Journals of Captain James Cook" edited by J C Beaglehole. These are weighty volumes, but the appendices contain exactly the sort of information which you are seeking.
By Cliff Thornton on 9/23/2014 3:40:36 PM Like:0 DisLike:1
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I really appreciate if I could be directed to the "equipment lists" of James Cook's 3 Pacific voyages as I am compiling a paper on Cook's surveying techniques on each of these journeys of exploration. Thank you very much.
Regards, John Brock, Registered Surveyor, Australia
By John Brock on 9/22/2014 2:52:23 PM Like:0 DisLike:1

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