PROJECTILES CONTAINING EXPLOSIVES A. E. 137 



continue to live in an atmosphere containing a very large proportion 

 of this latter gas. 



Let us now examine the nature of the phenomena produced by 

 the rupture of the metallic envelop constituting the body of the shell. 



Different cases are distinguished according as to whether th^body 

 consists of cast iron or of steel. In the first case the metal is, as 

 it were, pulverized by the explosive. The metallic powder produced 

 by the explosion is projected with a great velocity; but, as the mass 

 of the pieces is extremely small, they rapidly lose their velocitj^; 

 in fact they have no efficiency after a course of a few meters. 



By reducing the ratio of the weight of the charge to that of the 

 projectile one can, it is true, somewhat improve the fragmentation. 

 They can not, however, obtain a satisfactory result except by reduc- 

 ing the weight of the charge to such an extent that the effects of 

 the blast and the momentum of the fragments become in themselves 

 insufficient. 



In addition to secure the necessary conditions of safetj^ the walls 

 of the cast-iron shell must be thicker than those of the steel shell, 

 from which it results that the former is inferior to the latter from 

 all points of view. 



The rupture of the steel envelop is effected from the begimiing 

 in a totally different manner from cast iron. If the body of the 

 shell is thin, it is torn into strips of relatively light weight. 



The destructive effect from the action of the gas on loose soil 

 manifests itself in the production of a cavity having the form of 

 an elongated ellipsoid whose longer axis will be perpendicular to 

 the horizontal projection of the trajectory. The difference in length 

 of the two axes diminishes, other things being equal, the greater 

 the depth to which the projectile has penetrated the ground before 

 its explosion. 



When the walls of the projectile are thicker the fragmentation 

 changes in character and they note the production in place of the 

 preceding chamfer strips, of fragments of irregular form, the aver- 

 age weight of which increases with the ratio of the weight of the 

 projectile to that of its charge. For a given projectile the size of 

 the pieces furnished by any part of it varies with the thickness of 

 the walls at that point. The velocity of these pieces naturally varies 

 inversely as their weight. This may be measured with the wire 

 screens and the chronographs. The results obtained will be but 

 average indications and often will be very inexact on account of the 

 fact that the wires of the screen targets are sometimes broken by the 

 shock wave before they can be cut by the fragments. Accepting this 

 necessary condition it has been observed that the velocity of the 

 fragments reaches and may surpass 1,200 meters per second when 

 using a shell with thin walls. 



