122 MEMOIR OF C. F. BEAUTEMPS-BEAUPRE. 



not meet, a series of approximations tending to modify in au admissible degree 

 the position of tlie ship at the different stations sufficed to establish the neces- 

 sary junction. The approximations in question might be made with still more 

 rigor by calculation, and one of our most scientific hydrographers, IM. de Tcssan, 

 has even shown that the method of least sqiiares is here applicable;* but M. 

 Bcaupre 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 i-cuders 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 Ave 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 

 Ci'uz, enabled M. Beaupru to give a remarkable proof of his skill in applying 

 these processes, Avhich 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. Beaupre has caused it to be engraved in the 

 19th plate of the atlas, with all his lines of construction, as au example of his 

 manner of operating, and it is here that he has explained his method with de- 

 tails at which Ave haA'C 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 A'oyage of d'Entrecasteaux, an appendix Avhich has become the vade-?necu?}i, 

 and, if 1 may so sjDeak, the catechism of the constructors of marine charts. 



In reducing to rule, and in practicing his method, M. Beaupre fulfilled the 

 most cherished Avish of the scientific hydrographers, Avho, at the close of the 

 eighteenth century, employed themselves Avith the means of giving to nautical 

 science all the precision of Avhich 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, Avhich 

 till then Avas 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 Avas requisite that some engineer of 

 a peculiar aptitude should devote himself Avith energy and perseverance to the 

 application of the ncAV instruments and rigorous geometric methods adapted to 

 the accurate measurement of angles. M. Beauprd proved fully equal to this 

 honorable mission, and, thanks to his unceasing efforts, the voyage of d'Entre- 

 casteaux inaugurated the opening of a ncAv era — that of precise hydrography. 

 Like all other branches of human knoAvledge, hydrography has been adAanced 

 by degrees. After the invention of the compass, so far surpassed at a later 

 stage by ^ew instruments, the discoveries of Christopher Columbus and of 

 Vasco de Gama gave ideas a Avholly new direction. Subsequently the adveu- 



* See Voyage autour du Monde, par Ic frigate Venus, coinmandee par 

 Thouars: Physique, par M. do Tessan, t. v., p. 233. 



M. Abel Dupetit 



