Capt. Say's Stereometer revived by Professor Leslie. 333 



Art. XXXIX.— DECISIONS ON DISPUTED INVENTIONS AND 

 DISCOVERIES. 



Professor Leslie's Apparatus for Ascertaining the Specific Gravity of ' Pow* 

 ders, not invented by him in 1826; but by H. Say, Captain of Engineers, 

 in France in 1797. 



In the year 1826 there appeared in the Annals of Philosophy, No. 64, 

 and in the Journal of the Royal Institution, No. 42, a drawing and descrip- 

 tion of an apparatus for ascertaining the specific gravity of powders said 

 to be invented by Professor Leslie. The editor of the Annals considers it 

 as a great boon to philosophers, and after its description, he adds : 



" Such is the professor's process, which appears to us remarkably in- 

 genious as well as beautifully simple, and we shall see from some of the 

 results which it has already afforded, that it must furnish important aid 

 to the natural philosopher in his researches." 



Although we should have been disposed to welcome such an auxiliary 

 from any part of the world, but particularly from our own good city, yet, 

 as the invention thus highly lauded, has been known in England and 

 France, and published in English and French, thirty years ago, without 

 having furnished any aid to the natural philosopher, we fear that its re- 

 vival, without one single improvement, or even change, is not likely to give 

 any new impulse to scientific inquiry. 



The preceding fact has been made known to the scientific world by Ba- 

 ron Ferrussac in his Bulletin des Sciences Math. Phys. et Chim. for De- 

 cember 1826, in the following notice. 



" On the Pretended Invention of Mr Leslie." — " From the Bull, des Sc. 

 Math, of September 1826, No. 117, we learn that Mr Leslie has invented 

 an instrument for measuring the density of powders. As the description 

 of this instrument agrees perfectly with that of the stereometer invented 

 twenty-nine years ago by a French engineer of great merit, who unfortu- 

 nately fell in Egypt, M. H. Say, it is proper to announce to Mr Leslie 

 that he has made a mistake in attributing to himself the honour of this 

 discovery, which he will find published, with drawings, and a complete de- 

 scription, in vol. xxiii. p. I of the Annales de Chimie for 1797. This in- 

 strument, too, having been actually executed, was often used in measuring 

 specific gravities, particularly that of gunpowder, and it still exists in the 

 collection of the Polytechnic School." 



After reading the preceding passage, we turned up the 23d volume of 

 the Annales de Chimie, and found that the invention published by Mi- 

 Leslie is perfectly identical with that described and drawn by Captain Say, 

 Mr Leslie's drawing is indeed an exact section of Fig. 3 of Captain Say's 

 paper, the tripod which contains the instrument and the frame which sup- 

 ports the pully for raising the lid, being left out in the professor's sketch. 



Captain Say remarks, that his instrument furnishes us with the means 

 of measuring the volume of liquid bodies, soft bodies, porous bodies, and 

 powders, as well as that of solids. His description of it occupies twenty- 



