VOL. LXXX.] PHILOSOPHICAL TRANSACTIONS. 547 



Count Saluce remarks,* that the elastic air generated by the inHammation ot 

 gunpowder occupies, when cold, 222 times the bulk of the powder ; which 

 agrees, as he finds, with the computation made by Messrs. Hauksbee, Amontons, 

 and Belidor. This calculation he confirms in the Melanges de Philosophic et 

 des Mathematiques de la Societe Royale de Turin, which is a continuation of 

 the former work. He is of opinion, that this elastic fluid is of the same nature 

 with common air, which was likewise the opinion of Dr. Hales ; and that the 

 prodigious force of gunpowder depends on the action of the fire on all its parts, 

 by which this fluid exercises all the force of its elasticity. 



The extrication of such a considerable quantity of a permanent elastic fluid bv 

 the firing of gunpowder has been put to a particular use by several philosopher?. 

 Mr. De La Condamine gives an account of a brass air gun contrived by one Mr. 

 Maty, of Turin ; which he loaded with air condensed by firing in it 2 ounces of 

 gunpowder, which, by its inflammation, let loose such a quantity of air as was 

 sufiicient to shoot a leaden bullet 6o paces, and to repeat the process 18 times, 

 the strength of the explosion diminishing gradually as in other air guns. 



In the learned work of Mr. Antoni, an Italian gentleman, I find the same 

 experiment, the account of which is accompanied with a figure of such an air 

 gun, in which the author fired 1 ounce of gunpowder, the barrel being very 

 stout, and of a size capable of containing 10 ounces. He afterwards let a 

 quantity of this compressed air out by a valve in the same way as it is done in the 

 common air guns. This 1 ounce of gunpowder yielded air enough to propel a 

 leaden bullet through aboard 3 lines thick, at the distance of 40 paces, and to 

 repeat the process 1 6 or 18 times. 



The difference of the quantity of elastic fluid obtained from the firing of 

 gunpowder by Mr. Robins and others might be owing to the difficulties attend- 

 ing the investigation, or to the different proportion of the ingredients used in the 

 composition of the powder ; as it is well known, that gunpowder for the use of 

 the army is made of 5 or 6 parts of nitre to 1 of charcoal, and 1 of sulphur ; 

 when 7 parts of nitre are used, it is called poudre d'artifice. 



Mr. John Bernouilli calculates the density of the air contained in a solid state 

 in gunpowder to be -toVb^ o( what this fluid is when it constitutes a part of our 

 atmosphere. But he does not consider this air as existing in all the component 

 ingredients of the gunpowder, but chiefly in the nitre: and Count Saluce sup- 

 poses, that that part of the gunpowder which contains this air constitutes a con- 

 siderable part of its bulk, though somewhat less than the half. Let us now 

 suppose, that part of the gunpowder which contains this air to be not much less 

 than the half of the whole mass ; for it would be difficult to demonstrate 



* Miscellanea Pliilosophico-Mathematica Societatis privatae Taurinensis, p. 125. — Orig. 



4 A 2 



