276 THE POPULAR SCIENCE MONTHLY. 



the vibrations of the gun, which, to some extent, rings like a bell. 

 This latter, I apprehend, will disappear at considerable distances." 

 The result of subsequent trial, as reported by General Campbell, is, 



Fig. 1. Breech-loading Fog-Signal Gun, with Bell-Mouth, proposed by Major Mait- 

 land, K. A., Assistant Superintendent. 



that " the sonorous qualities of bronze are greatly superior to those of 

 cast-iron at short distances, but that the advantage lies with the baser 

 metal at long ranges." ' 



Coincident with these early trials of guns at Woolwich, gun-cotton 

 was thought of as a probably effective sound-producer. Theoretic con- 

 siderations caused me to fix my attention persistently on this substance ; 

 for the remarkable experiments of Mr. Abel, whereby its rapidity of 

 combustion and violently explosive energy are demonstrated, seemed 

 to single it out as a substance eminently calculated to fulfill the condi- 

 tions necessary to the production of an intense wave of sound. What 

 those conditions are we shall now more particularly inquire, calling to 

 our aid a brief but very remarkable paper, published by Prof. Stokes 

 in the Philosophical Magazine for 1868. 



The explosive force of gunpowder is known to depend on the sudden 

 conversion of a solid body into an intensely heated gas. The work 

 which the artillerist requires the expanding gas to perform is the dis- 

 placement of the projectile. Such, however, is not the work that we 

 want our gunpowder to perform. We wish it to transmute its energy 

 not into the mere mechanical translation of the shot, but into vibratory 

 motion. We want pulses to be formed which shall propagate them- 

 selves to vast distances through the atmosphere, and this requires a 

 certain choice and management of the explosive material. 



1 General Campbell assigns a true cause for this difference. The ring of the bronze 

 gun represents so much energy withdrawn from the explosive force of the gunpowder. 

 Further experiments would, however, be needed to place the superiority of the cast-iron 

 gun at a distance beyond question. 



