414 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



the left hand side of the same fig'uve is a rear elevation, both with a part 

 of the shell removed, to show the interior arrangement. 



Tiie enlargement of the bore of this gun, by pressure of the powder, 

 would require, therefore, the overcoming of the inertia of the weight of a 

 frustum of a cone, without compressibility from each square inch of sur- 

 face against which the pressure of the powder is exerted. The projectile 

 being a cylinder, slightly elastic and compressible, its inertia would be 

 more readily overcome than any frustum of a cone of the metal of the gun; 

 having equal area at the surface of the boi'e, against which the pressure of 

 the powder is exerted, its inertia would have to be overcome almost in- 

 stantly throughout its whole length, because of its resistance to further 

 compression ; while the inertia of the shot would be overcome gradually, or 



in successive disks of its length, because ot its undiminished compressi- 

 bility. The addition of the tensile strength of the metal makes it probable, 

 therefore, that this gun cannot be burst by the pressure of the powder, if 

 the shot is free to move forward. I suppose this gun has sufficient length 

 of caliber to utilize nearly all the expansive force of quick-burning powder, 

 the cartridge occupying not more than one-fifth of its length of bore. 



The spherical form is an advantage, by allowing the gun to be simply 

 rotated on its trunnions, in order to be loaded without exposing the men 

 by the presence of any open port hole; and it is so nearly balanced upon its 

 trunnions H, as to be worked with ease, notwithstanding its weight, fifty-one 

 tons. It graduated on its periphery, for adjustment to the proper elevation. 



The following illustration shows a pair of guns mounted in a turret, for 

 a fort or water battery. The manner of mounting and operating is such 

 as to allow them to be loaded without exposing the men to receive missiles 



