whence 



ON RIFLED GUNS. 21 



W 0.6989700 



V 2 6.1938200 



I a c 9652513 



g ac 8.4948500 



or 



2;> = 22537lbs 4.3528913 



^>= 1126S.fi lbs., over five and a half tons, 

 which, being an average, is much below the maximum. It is the pressure upon that layer of 

 powder in contact with the bottom of the shell. The inner diameter of the shell is about 

 three-tenths of afoot, and the area over which the pressure is exerted is, therefore, about 

 seven-hundredths of a square foot. The pressure is found to be sufficient to destroy all 

 granulation and to reduce the powder to a compact indurated mass at the bottom of the shell 

 hard enough to resist all effort by the finger-nail to impress it. Of course, in all this there is 

 much friction among the particles of the powder, and great condensation of air at the base of 

 the projectile's cavity. 



The pressure is greater in proportion as the bursting charge is greater and the area of 

 the cross section of the shell's cavity is less. It is found that the explosions within the gun 

 are much more frequent for larger than smaller charging. Fuze charges — that is, charges just 

 sufficient to blow out the fuze plug without breaking the shell — are rarely attended with inter- 

 nal explosions. 



PART II. 



MATERIALS AND DIMENSIONS OF GUNS. 



(1) — It has been shown that the principle of rifling is, of itself, no sufficient cause of the 

 disasters which have characterized some of our artillery practice, and that if these disasters 

 did not wholly arise from sh eer carelessness, as many doubtless did, the source of trouble 

 must be sought outside of the mere fact of rifling. 



(2) — It does not appear that the propagation of molecular disturbance, by Avhich alone 

 the forces of resistance to the expanding action of gases are developed and hrought into action, 

 has ever been duly considered in the choice of the material and adjustment of the dimensions 

 of guns, and yet it is of all considerations the most important. 



In the preceding pages an attempt has been made to construct a set of formulas by which 

 to compute the strains upon rifled guns. It is now proposed to indicate the influence which 

 the rate of molecular disturbance has upon the capacity of a gun to resist the more important 

 of these strains, called the circumferential. 



(3) — It is well known that the velocity of molecular distur bance is in nowise dependent 



upon the intensity of the initial forces which produce it, but results wholly from peculiarity 



of molecular structure that determines elasticity and density. This velocity is always the same 



in the same body; and a body to preserve its identity, in this connexion, must preserve its 



temperature and the external pressure upon it unchanged. The material of a gun after 



(333) 



