384 Professor Leslie on the Coniometer. 



On the Co7iiometer. In a Letter from Professor Leslie to 

 Professor Jameson. 



My Dear Sir, 



XXaving just seen a paragraph in the Annals of Philosophy 

 for March 1827, copied from the Annales de Chimie et Phy- 

 sique, in which my contrivance of an instrument to measure the 

 specific gravity of powders is reclaimed for M. Say, Captain of 

 Engineers, who, it seems, perished in the famous Egyptian Ex- 

 pedition ; I trust you will allow me to offer some explanation. 



I was aware that attempts had been made to apply the 

 law of Mariotte, in ascertaining the specific gravity of a sub- 

 stance which could not be immersed in water, but supposed them 

 to have proved unsuccessful ; and all this I stated at the time 

 to the persons who witnessed my experiments. When I first 

 visited Paris in 1802, my kind friend the late M. Guyton-Mor- 

 veau shewed me an apparatus for that purpose ; and it then ap- 

 peared to me very clumsy and unmanageable. I have no recol- 

 lection of the nature of its construction, and only a sort of faint 

 impression that it was somehow connected with an air-pump. 

 Indeed, were it worth while, I could easily point out two several 

 methods of discovering, by help of a good air-pump, the abso- 

 lute bulks, and consequently the specific gravities, of powders 

 and very porous substances. 



I have now looked into the article referred to in the 23d vo- 

 lume of the Annales de Chimie, and will most readily admit, that 

 the Stereometer of M. Say is substantially the same as my Coni- 

 ometer. But of this coincidence I .was quite unconscious, when 

 I designed my instrument. I made no boast of discovery, and 

 only mentioned it as a simple contrivance, which could be di- 

 rected to some very useful and curious researches. I permitted, 

 indeed, a gentleman who admired its application, to draw up a 

 popular description of it in his own way ; but I deferred giving 

 any account of it myself, till I had brought it to greater perfec- 

 tion, and was enabled to produce a series of correct and inte- 

 resting results. So little, however, did it engage my attention, 

 that I have suffered it to remain nine months for alteration, in 

 the hands of the artist. A year has nearly elapsed before any 

 chemical philosopher has challenged its originality ; and Dr 



