508 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



55,000 atmospheres; but, as the charges filled but a portion of the cavity 

 beneath the weight, he infers that the maximum pressure in a space entirely 

 filled with the powder ought to be as high as 101,000 atmospheres. 



The processes and results of Rumford are criticised by Piobert (Traite 

 d'Artillerie, Paris, 184T), who regards them as unsatisfactory. According 

 to his own determination, the maximum pressure should be about 7500 at- 

 mospheres. 



Dr. Young, in his lectures on natural philosophy, quotes Euber, Lombard 

 and D. Bernoulli, as giving for the same pressure the value of 10,000 at- 

 mospheres. He, himself, seems to favor a higher estimate, between 30,000 

 and 50,000 atmospheres. In Nichols Cyclopedia of the Physical Sciences, 

 tinder the article "Gunnery," we find this statement: "Various experi- 

 ments indicate the expansive force of gunpowder to be between 25,000 and 

 32,000 atmospheres." No authorities are cited. In volume 22, second se- 

 ries of this journal, is contained an article on the " Pressure of Fired Gun- 

 powder," by W. E. Woodbridge, M. D., in which are detailed the results of 

 some interesting experiments made by the writer, in connection with Maj. 

 Mordecai, U. S. A., at the Washington Navy Yard, upon the pressure which 

 guns actually endure in firing round shot. These experiments are deserv- 

 ing of study, and will be examined hereafter; but they are not to the point 

 immediately before us. 



Mr. Woodbridge, however, states that he exploded twenty grains of rifle 

 powder in a cast steel cjdinder, capable of enduring a pressure of 6200 at- 

 mospheres at the maximum — the powder entirely filling the cylinder, and 

 the explosion being efl'ected without escape of gas, without bursting the 

 cylinder. Mr. Woodbridge also c]U(jtes Gen. Antoni, of the Sardinian army, 

 as authority' for the statement that fine military powder, fired in a cylinder 

 of half an inch diameter and height, with no opening but the vent through 

 ■which it is fired, exerts a pressure of 1400 to 1900 atmospheres. 



In the Encyclopedia Britanica, last edition, article gunpowder, Mr. Tora- 

 Hnson, assuming that the gaseous products of the combustion of gun-pow- 

 der are carbonic oxyde, sulphurous acid and nitrogen, exclusively, com- 

 putes a theoretic enlargement of volume as 1:787 3. Assuming further 

 that the elevation of temperature is such as to treble this volume, he makes 

 tlie maximum pressure 2360 atmospheres. 



The interesting reports of Capt. Rodman upon metals for heavy guns, 

 and upon the qualities of cannon powder, published in 1861 by authority of 

 the Secretary of War of the Unitc-d States, contain statements of experi- 

 ments in which powder was actually exploded in a shell which it could not 

 burst, but which it entirely filled, and of the force actually developed under 

 these circumstances. In these experiments there was an orifice, one-tenth 

 of an inch in diameter, through which the powder was fired, and through 

 which the gases might of course more or less rapidly escape. The highest 

 pressure registered by the gauge emplo^^ed for the purpose, contrived by 

 Capt. Rodman himself, and described in the volume, was 185,000 lbs. per 

 square inch, equivalent to more than 12,000 atmospheres. For certain 

 reasons which he mentions, Capt. Rodman thinks that this is below the 

 true pressure, so that he concludes, " I should feel perfectly safe in fixing 



