B O R D A. 



719 



Borda. nious experiments and ohscrtationt oil tlie motion of 

 "-""V "' fluids through different oriiices. He prepared a theo- 

 ry of the motion . f fluids different from that which 

 had been given by Bernoulli and D'Alembert, and 

 he made new experiments on the vena contractu. 



In the year 1767, he published an excellent disser- 

 tation in the Memoirs of the Academy, entitled, JVfe- 

 moires sur les Roues Hi/draulir/tws. In that valuable 

 paper he has shewn, that an undershot wheel pro- 

 duces a maximum effect when its velocity is one-half 

 that of the current, though in practice the velocity is 

 never more than three-eighths that of the current. 

 He proved, after Deparcieux, from theory, before 

 Smeaton had determined it by experiment, that the 

 effect of overshot wheels increases with the slowness 

 of their motion ; that they are capable of raising, 

 through the height of the fall, a quantity of water 

 equal to that by which they are driven ; that under- 

 shot vertical wheels produce only three-eighths -of this 

 effect; that horizontal wheels produce about one- 

 half of this effect with plain floatboards, and a little 

 more than one-half with curvilineal floatboards. 



This memoir of Borda was followed by another, in 

 1768, on the construction of water-pumps. About 

 this time his attention was directed to isoperimetrical 

 problems, and he had the honour of obtaining the 

 same results as Lagrange, though by a different me- 

 thod. 



The last work of our author, which appeared in 

 the Memoirs of the Academy, was a dissertation on 

 the Theory of Projectiles. The immense differences 

 between the theory and the experimental results 

 which had been obtained on this subject, stimulated 

 the ingenuity of Borda. He found, that the range 

 of a twenty-four pounder was diminished nine-tenths 

 by the resistance of the air ; and that the diminution 

 would be still greater when the flight of the ball was 

 opposed by wind ; and he has formed a table, shew- 

 ing the results calculated for pieces of all calibres, 

 for all angles of elevation, and for various ranges and 

 degrees of velocity. 



The success and utility of the labours of Borda 

 brought him under the particular notice of M. Pras- 

 lin, the minister of marine, who was anxious to have 

 the benefit of his talents in the French navy. The 

 practice of the service, however, opposed such a plan, 

 and the officers of the navy naturally resisted a mea- 

 sure which might ultimately prove injurious to their 

 own interests. But M. de Praslin had taken his re- 

 solution : He considered the brilliancy of Borda's ta- 

 lents as entitling him to an exception from general 

 usage, and he therefore appointed him sub-lieutenant 

 in the navy. 



Borda made his first appearance in his new profes- 

 sion in the year 1768, but, till the year 1771, no 

 events occurred which are deserving of notice. The 

 prizes which were at this time offered, both in Eng- 

 land and France, for the improvement of chronome- 

 ters, to find the longitude at sea, naturally produced 

 in both countries a great variety of inventions. The 

 French government having determined to try the ac- 

 curacy of some of these time pieces, and of other in- 

 struments which were subsidiary to the grea' object 

 of finding the longitude, the Academy of SeienC' 

 appointed Borda and Pingre as commissioner, 



making these trials ; and they were ordered to sail 

 in the Flora frigate, under the command of Ver- 

 dun de la Cranne. This voyage was performed in 

 the years 1771 and 1772, during which they touched 

 at various places in Europe, Africa, and America, 

 and completely fulfilled the objects for which they 

 were sent out. An account of this voyage was pub- 

 lished at Paris in 1778, in 2 vols. 4to, entitled, 

 Voyage fait par ordre da Roy en 1771 et 1772, &c. 

 A shorter accoant of the results obtained during the 

 expedition will be found in the Memoirs of the Aca- 

 demy for 1773. 



- The y.eal and success with which Borda had per- 

 formed his part in this expedition, pointed him out as 

 the fittest person to be employed in determining the 

 position of the Canary Isles. With this view he was 

 promoted to the rank of lieutenant in 1775, and in 

 the year following he set sail in the frigate La Bous- 

 sole, having under his orders the Espiegle, command- 

 ed by M. de Puysegur. During this interesting 

 voyage he determined the relative and absolute posi- 

 tion of the Canary Isles, by means of several points 

 taken on each, and on the coast of Africa. He veri- 

 fied the height of the Peak of Teneriffe, and calcu- 

 lated tables for finding the position of a ship at sea 

 from the apparent height of this mountain. He ex- 

 amined the peak itself with great care, and brought 

 home with him several mineralogical specimens. 



M. Borda was appointed major-general to the naval 

 armament' which sailed from Toulon under the Count 

 D'Estaing, and he was present with that distinguish- 

 ed commander at all the naval operations, by which 

 he contributed to the final emancipation of America. 

 In this high situation, the wisdom, prudence, and in- 

 tegrity of Borda excited the admiration of his fellow 

 officers. 



From the experience which he had now obtained 

 of the naval service, Borda perceived many defects 

 in the construction of vessels, which could easily be 

 remedied. He considered the want of uniformity in 

 the construction of ships which were to act together 

 as a great defect, from which arose a great discord- 

 ance in their movements, and in the execution of sig- 

 nals. Upon his return to France, he communica- 

 ted this idea to the government, who immediately 

 resolved to carry it into effect. The best form for 

 a ship of 74 guns was selected by Borda from a va- 

 riety of constructions, and was made the model for 

 the formation of others ; and the same plan was fol- 

 lowed for vessels of different rates. 



In the year 1781, Borda was appointed to the 

 command of the vessel Le Guerrier ; and in the year 

 1782, he obtained the command of the Solitaire, a 

 ship of 64 guns, for the purpose of escorting a body 

 of troops to the island of Martinique, at a time when 

 the reduction of all our West India islands was the fa- 

 vourite object of the allies, and when they had ac- 

 tually succeeded in the capture of the islands of 

 Nevis and ot Christophers. Borda hud the good for- 

 tune to convoy die troops under his orders to their 

 final destination ; and having joined the fleet under 

 tne Count De Grasse, he was ordered to a cruising 

 n with, ti'c I'ois.mand of several frigates. After 

 .- 'V !>u r n ,.': SWt, ; thick fog came on, 

 j i.'.J nis little 



Borda. 



