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on board, could not be taken with too much rapidity, for it was necessary that the ship should not materially change its place during the time of the operation. The principal operations which serve as a foundation for the charts constructed by M. Beaupré are such as were executed either at midday, or simultaneously with the observations of horary angles; that is to say, at such times : of each day as the position of the vessel was determined by astronomical observations and the chronometer. On these occasions he assembled around him the greatest possible number of observers, and he had found or formed a great many among the officers of the frigate. Just one minute before taking the observations he made a sketch of the coast under view, beginning with those parts of it which, being most remote, would undergo least change of outline by reason of the movement of the ship; then, precisely at the moment when the astronomical observations were taken, he measured the angular distance between the object which he had designated to his assistants as the point of departure and one of the remarkable places of the coast, while each of the assistants measured the angular distance of the same point of departure from one of the other objects embraced in the survey. The results of these simultaneous observations were afterwards transferred to the sketch which had been made of the outline of the land. All the angular measures were taken with Borda's repeating circle. When the sun was not too high above the horizon, one of the observers measured the distance of that body from one of the remarkable points of the coast; by means of the heights of the sun observed at the same moment by M. de Rossel, and from the distance measured, M. Beaupré obtained the astronomical bearing of that point, whence he deduced the bearing of all the points between which angles had been taken. Two compasses were always directed, during the observations, on the place chosen as a point of departure for the angles, and the mean of the bearings given by those instruments was transcribed in the collection of notes, and this whether an astronomical bearing had been obtained or not. In the first case the magnetic indication served to show the variation of the needle, and in the second to supply, though imperfectly, the absence of an astronomical observation. If circumstances, which, however, occurred but rarely, prevented the co-operation of a sufficient number of observers to take simultaneously the angles of all the remarkable points necessary to be determined, M. Beaupré arranged several circles of reflection, so that each observer might promptly take two or three angles, without being obliged to write them on the spot; and these observations, made with a rapidity proportionate to the expertness of the observer, were found to agree almost as exactly as those made simultaneously. M. Beaupré, who drew the chart with as much facility as exactness, found a marked advantage in embodying the results observed as promptly as possible, for he had then all the circumstances of the observations present to his mind. It was not seldom that he was enabled in this way to detect and remedy inadvertencies committed in writing the angles measured. The precision of his graphic constructions ever rendered it practicable for him to verify, and sometimes to correct, with great probability, the positions of the ship, determined several times a day by astronomical observations, combined with the indications of chronometers and the estimate of courses. The means of verification resulted, in part, from the fact that the observations of each station gave him a series of visual lines, springing essentially from the same point, and forming known angles, whether with one another or with the astronomic meridian, or at least with the magnetic meridian, itself determined by an observation made at nearly the same time. . They resulted, moreover, from the circumstance that all the visual lines directed from different stations on the same object, such as a cape or a mountain, must, on the draught, intersect one another at the representation of that object. When, at the first trial, these did
not meet, a series of approximations tending to modify in an admissible degree the position of the ship at the different stations sufficed to establish the necessary junction. The approximations in question might be made with still more rigor by calculation, and one of our most scientific hydrographers, M. de Tessan, has even shown that the method of least squares is here applicable ;* but M. Beaupré adhered generally to the graphic method, which he employed with as much sagacity as precision.
The application of this rigorous method fixes the position of the principal points of the chart about to be constructed, as the tops of mountains, capes, &c. The details, such as the outline of coasts, course of rivers, &c., are afterwards described with such degree of precision as time permits; and when a sojourn of some duration renders it practicable to add the soundings taken at sea, as was the case in regard to the straits of d'Entrecasteaux and other parts of the coasts of Van Diemen's Land, the positions of the points of sounding are fixed by reference to the principal points determined by the bearings, in accordance with the methods which will be presently indicated when we arrive at the hydrographic surveys of the coasts of France.
The bearings taken from the 19th to the 23d May, in the archipelago of Santa Cruz, enabled M. Beaupré to give a remarkable proof of his skill in applying these processes, which were then new. Faithful to his method of constructing, day by day, the chart of those parts of coasts which he would not again see, he devoted the night of the 21st to describing the details of the south coast of the island of Santa Cruz; that of the 22d was similarly occupied with the north coast; and, the ships sailing on the 23d for the Solomon islands, he applied himself, as soon as the land was lost sight of, to the definitive reduction of his chart. This, like all the rest belonging to the voyage of d'Entrecasteaux, was constructed on a scale of three lines for one minute of the equator; and as it presented, for the discussion of which we have been speaking, nearly all the cases to be met with in practice, M. Beaupré has caused it to be engraved in the 19th plate of the atlas, with all his lines of construction, as an example of his manner of operating, and it is here that he has explained his method with details at which we have only been able to give a cursory glance. They may be seen in the appendix relative to this subject at the end of the first volume of the voyage of d'Entrecasteaux, an appendix which has become the vade-mecum, and, if I may so speak, the catechism of the constructors of marine charts.
In reducing to rule, and in practicing his method, M. Beaupré fulfilled the most cherished wish of the scientific hydrographers, who, at the close of the eighteenth century, employed themselves with the means of giving to nautical science all the precision of which it is susceptible. Borda, after having placed in the hands of navigators the repeating circle of which they still make use, had recommended its employment in preference to the compass, which till then was exclusively relied on for surveys executed at sea. Flurieu had equally recommended astronomic surveys. For naturalizing these scientific processes in the practice of hydrography, it was requisite that some engineer of a peculiar aptitude should devote himself with energy and perseverance to the application of the new instruments and rigorous geometric methods adapted to the accurate measurement of angles. M. Beaupré proved fully equal to this honorable mission, and, thanks to his unceasing efforts, the voyage of d'Entrecasteaux inaugurated the opening of a new cra—that of precise hydrography.
Like all other branches of human knowledge, hydrography has been advanced by degrees. After the invention of the compass, so far surpassed at a later stage by new instruments, the discoveries of Christopher Columbus and of Vasco de Gama gave ideas a wholly new direction. Subsequently the adven
* See Voyage autour du Monde, par le frégate Venus, commandée par M. Abel Dupetit Thouars: Physique, par M. de Tessan, t, V., p. 238.
turous circumnavigations of the Magellans, Mendañas, Drakes, Tasmans, and Dampiers, made known the |. outlines of the two oceans, but with very imperfect exactness, as may be perceived from a glance at the old globes which are still of frequent occurrence in Paris. That, according to the happy expression of M. Willemain, was the heroic age of the navigation of discovery; the modern Argonauts went forth in their search for the golden fleece with an ardor little favorable to systematic exploration, and which yet did not prevent them from overlooking the rich auriferous deposits of California and Australia. Towards the middle of the eighteenth century, after Buffon had published his Natural History, the taste for voyages was revived under a form even then much more scientific. In the course of a few years we see Byron, Carteret, Wallis, traverse the Pacific ocean, and make the tour of the world. Cook is sent to Tahiti to observe, June 3, 1769, the passage of Venus over the disc of the sun. He makes two other important voyages, and after having traversed the Pacific in all directions, and penetrated into the frozen regions of both poles, falls in 1779 beneath the weapons of the natives of the Sandwich islands. Cook remains the principal figure and characteristic of this period; but had fate permitted the instructions given to la Perouse to have been completely carried out, the voyage of this last would, perhaps, have afforded the best example of what it was possible to accomplish with the hydrographic methods then in use. These different enterprises made known almost all the lands and archipelagos with which the ocean is strown, and furnished charts which already presented their general form with a great degree of fidelity. Last come the hydrographic voyages of precision. If the expedition of d'Entrecasteaux offers the first example of them, the voyage of the Coquille, executed under the command and published under the direction of our distinguished colleague, Captain Duperrey, must, perhaps, be regarded as the most perfect type of this class of enterprises. To the same class belong the almost too hazardous voyages of Sir John Ross among the ices of the antarctic pole, and those not less daring of M. Dumont d'Urville. The hydrographic study of the archipelago of Santa Cruz, which retained around M. Beautemps-Beaupré some of the most skilful officers of the frigate, did not so exclusively occupy the attention of Admiral d'Entrecasteaux and other chiefs of the expedition as to divert their attention from the main object of their mission, which was to seek for traces of la Perouse. They constantly communicated with the shores, questioned the natives, examined the objects in their possession, and observed, among other things, a piece of iron from the hoop of a cask, set as a hatchet; but no one then suspected that there was here a vestige of the expedition of la Perouse. The admiral has minutely recorded the reasons why no importance was attached to the circumstance. Nevertheless the chart of the archipelago of Santa Cruz presents, in its SE. portion, an island on which by a rather singular chance the admiral bestowed the name of la Recherche, after that of his own frigate sent in search of la Perouse. “We took the bearing of this island, says M. Beautemps-Beaupré, for the first time from our point of station at 20 minutes after 9 o'clock, 19th May, at a great distance, At noon, the same day, we again took its bearing, and then lost sight of it.” Situated at the southeast extremity of the archipelago of Mendaña, this island has been in like manner seen and lost sight of by not a few other navigators in whose track it lay, and who little imagined that la Perouse and his companions had paid with their lives for the honor of having previously discovered it. Thus two years earlier than d'Entrecasteaux, Captain Edwards, commanding the English frigate Pandora, had discovered, August 13, 1791, this same island, which he had named Pitt island, and had sailed around its southern shore without suspecting that it concealed the remains of a world-renowned shipwreck. Thirty years later, in 1823, Captain Duperrey, among whose officers was M. Dumont d'Urville, passed in the corvette la Coquille, 2d and 3d August, at about half a degree to the W.S.W. of the island. Strong eastwardly winds prevented him from approaching nearer, but he took numerous bearings which served to rectify the position of the island, and then obeyed without thought the wind which bore him away from it, having himself no reason for supposing that this obscure spot presented any trace of the expedition of la Perouse. Yet the veil was about to be withdrawn. Four years after, in December, 1827, and January, 1828, M. Dumont d'Urville was lying with the Astrolabe in the port of Hobarttown, situated in those parts of Van Diemen's Land which MM. d'Entrecasteaux and Beautemps-Beaupré had surveyed with so much care while they were still desert. Here reports reached him, vague indeed, and even contradictory, respecting a surprising discovery made by Captain Dillon, commanding an English vessel, engaged in commerce. This mariner, it was said, had acquired authentic information relative to the shipwreck of la Perouse, and had even brought away the handle of a sword which he claimed to have belonged to that celebrated navigator. Notwithstanding the slight authority for these reports, M. Dumont d'Urville thought himself justified in modifying the route which his instructions traced for him. He touched, February 10, at Tikopia, where he found among the natives a lascar named Joe, a sailor and native of Calcutta, who was the same that had sold the sword-handle to Captain Dillon. This man, after a little hesitation, acknowledged that some years before he had gone to the Vanikoro isles, which are no other than the group of la Recherche, where he had seen many objects belonging to the vessels of la Perouse; that he had been then told that two very aged whites were still alive, but he himself had not seen them. The next day, February 11, 1828, the Astrolabe sailed for the Vanikoro islands, situated, according to the natives, about forty leagues W.N.W. from Tikopia. The vessel came to anchor, February 14, at the place of its destination, and remained till the 17th of March. M. Dumont d'Urville, being quite seriously indisposed, could not quit the corvette, which, besides, was, in more than one respect, not considered in entire safety; but, after having interrogated the natives, he despatched in succession several parties commanded . responsible officers, with whom he associated his faithful surgeon, M. Gaimard, whose recent death has been a new occasion of sorrow to the friends of science. The chain of reefs which, at a distance of two or three miles, forms an immense girdle around Vanikoro, closely approaches the southern coast near Pajou, in front of a place called Ambi. Here it is but a mile off, and it was here that, on a first visit, the native who preceded M. Jacquinot stopped his canoe in an opening between the breakers, and made a sign to the Frenchmen to look beneath the water. There, at a depth of twelve or fifteen feet, were clearly distinguishable, scattered here and there, and imbedded in corals, anchors, cannons, bullets, and divers other objects, especially numerous sheets of lead; the wood had entirely disappeared. The position of the anchors seemed to indicate that four of them had sunk with the ship, while two others had probably been let go. On a second visit M. Guilbert succeeded in withdrawing from the reefs the following objects: An anchor of about eighteen hundred oi. weight, without a stock, much rusted and covered with a crust of corals apparently from one to two inclies in thickness; a cast cannon, likewise covered with corals, and so much oxydized that the metal readily yielded under the hammer; a small swivel of brass and a blunderbuss of copper in much better preservation, one bearing on its trunnions 54S as its number, and 144 as its weight; the other 286 and 94 for its number and weight respectively, with no other marks; a pig of lead and large sheet of the same metal, together with some fragments of porcelain. The remains of a kettle had been previously procured at Nama, a village of the coast.
The following is the amount of the information obtained from the natives: About forty years previous to 1828, (which would carry us back to 1788, the date of la Perouse's disappearance,) one morning, at the close of a very dark night, during which the wind blew with violence from the SE., the islanders suddenly descried on the southern coast, opposite the district of Tauema, an enormous pirogue, stranded upon the reefs. It was rapidly demolished by the waves, and so entirely disappeared that nothing was ever recovered from the wreck. Of the persons who manned it a few only succeeded in escaping in a boat and gained the shore. The following day, likewise in the morning, a second pirogue, similar to the first, was discovered on the rocks before Païou; where, in the lee of the island, and less racked by the wind and sea, stranded moreover on a level shelf of twelve or fifteen feet depth, it remained some time in its position without being destroyed. This, Hke the first, bore a white ensign. The strangers who manned it landed at Palou, where they established themselves with those saved from the other ship, and immediately set about constructing a small vessel from the fragments of the ship which had not gone down. Their task was completed in six or seven moons, and, as most of the savages averred, all the strangers left the island. A few, however, declared that two remained behind, but that these had not long survived. M. de Fromelin, who also visited these shores in 1828, on the corvette la Bayonnaise, and who had doubtless heard of the discovery of the English Captain Dillon, ascertained by examination the existence of the remains of the French frigate on the reefs of Vanikoro. It was a source of regret to M. Dumont d'Urville that he had not been able, in 1828, to visit in person the place of the shipwreck; hence, when on a last and memorable expedition he traversed anew the great ocean, he caused his ships, the Astrolabe and the Zelée, to lie to, 6th November, 1838, near the yeef of the southern shore of Vanikoro. Landing in a sea too rough to admit of stopping on the reef, he discovered a space cleared of trees, which appeared to him to have been the spot where the parties from the wreck had pitched their camp. Near it he observed a large cocoa-nut tree which had been deeply cut around the trunk at two metres above the ground, besides other traces of the use of the axe at a remote date, but beyond this he noticed no new indications. The two frigates mounted with cannon, which could be none but those of la Perouse, for no others were known to have disappeared in these seas, had doubtless encountered, but with more adverse fortune, casualties similar to those which befell the frigates of Admiral d’Entrecasteaux; of which one was near being lost on the Beaupré islands at the time of their discovery, and the other struck on a reef of zoophytes in the pass which forms an entrance to the haven of Balade, but was fortunately extricated. It was not an impossibility that the remnant of the crews of la Perouse should be saved in the bark which they had constructed, and on which they put to sea about the close of the year 1788. In fact, the English Captain Bligh, of the ship Bounty, abandoned in the midst of the South sea by his revolted crew, in an undecked shallop only twenty-two feet in length, passed, 18th May, 1789, about fifty leagues to the south, and consequently almost within sight of the isles of Vanikoro, and succeeded, May 29, in reaching the coast of New Holland at the south entrance of Torres' straits, whence they made their way to CouPang, in the island of Timor. True it is, as apoears from the romantic narrative of his adventures, that not to have perished a hundred times was due only to the most astonishing good fortune. This fortune was denied to la Perouse and is companions, though the boat in which they left Vanikoro but a few months efore was no doubt larger and better appointed than that of Bligh. In similar circumstances many others . succeeded in being saved. In reading the stirring recital of their various perils, we readily perceive that in the fate of la Perouse there is nothing enigmatical; nor can the conclusion escape