PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 511 



Prof. Barnard proceeds to find tlie value of v^ and afterwards to find the 

 value of F, as compared with gravity, p representing the initial pressure 

 of the gases .in atmospheres estimated at 14.72 lbs. per square inch, Ws 

 the weight of a shot, Ss its specific gravity, u its' diameter in a fraction of 

 a foot, ^Yp tlie weight of the powder, Sp its specific gravity, 62.5 lbs. the 

 weight of a cubic foot of water, G the force of gravity represented by a 

 velocity of 32 1-6 feet per second, c the calibre of the gun in a fraction of 

 a foot, L its length of bore in calibres, I the length of the cartridge, and n 

 the ratio of the weight of powder to the weight of shot. After presenting 

 a series of equations from which the required values are deduced, (here 

 omitted for want of time,) the professor proceeds as follows : We will now 

 attend for a moment to the method of deducing the value of p, apiiori. . 



The materials emploj'ed in the manufacture of gunpowder are mixed 

 nearly in the proportion of one equivalent of saltpetre, one equivalent of 

 scalphnr and potassium, and three equivalents of carbon. If, in the com- 

 bustion, the sulphur and potassium be supposed to combine, we ma}' assume 

 the results to consist of one equivalent of sulphid of potassium, one equiva- 

 lent of free nitrogen, and three equivalents of carbonic acid. One grame 

 of powder will furnish, at 0° C of temperature, and mm .160 of pressure, 

 82"50 c. c. of nitrogen, and 248"40 c. c. of carbonic acid; in all, 330'92 c. c, 

 in volume of gaseous products. Any other probable combination of the 

 gaseous elements will not increase this volume. The investigation of 

 Messrs. Bunsen and Schischkoff demonstrate, however, that the sulphid of 

 potassium forms but a small portion of the fixed residuum. The sulphur iSj 

 to a great extent, oxydized, and forms sulphate and sulphite of potassa, 

 and a portion of the carbonic acid unites with the same base. A small 

 portion of the nitrate appears also to be nndccomposed. One grame of 

 powder, accordingly, furnishes but 193'1 cubic centimetres of gas. 



. The gunpowder employed by these experimenters contained an excess of 

 saltpetre above the theoretic proportion, and a deficiency of carbon. The 

 sulphur was also somewhat deficient, and there was about threc-and-a-half 

 per cent, of oxygen and hydrogen nearly in the proportions to form water. 

 The gaseous products constituted 0-3138 of the total weight, and the solid 

 residuum 0-6804. 



In the gunpowder employed in the American military service, the salt- 

 petre is slightly in excess, and also the carbon, the sulphur being in defi- 

 ciency. It is probable that the results of its combustion would vary some- 

 what from those here detailed, but not to such an extent as very materially 

 to affect the calculations which follow. In experiments of the Heidelberg 

 investigators, the gunpowder was burned under the ordinary pressure of 

 the atmosphere. It may be objected that, in the chamber of a gun, other 

 forms of a combination of the elements may take place; but, though this 

 is possible, it is hardly supposable that greater poM^er would, in such a 

 case, be developed. A combustion which should produce a greater volume 

 of gas would probably be attended with a less development of heat; so 

 that as much as would be gained in elastic force by one of these circum- 

 stances, would be lost by the other. 



The specific gravity of the fixed residuum at 18° C, was found to be 2-85. 

 By a method of determination devised by the experimenters, which is not 



