the pressure and velocity being High, and the quantity of 

 the gas evolved small. 



The exhaust from a steam engine is different in charac- 

 ter from that of a gas engine, even w^hen the exhaust 

 pressures and cylinder volumes are the same. The gas 

 engine, without a silencer, gives a sharper sound of much 

 less volume than the steam engine, the reason being that 

 the steam, being loaded with particles of Waaler, moves 

 much more sluggishly and gives a more prolonged impulse 

 to the surrounding air. This sluggishness considerably 

 increases the back pressure on the piston. 



With black powder, the gases as they leave the muzzle 

 bear a distinct resemblance to exhaust steam, being loaded 

 with solid or liquid particles, and are therefore sluggish 

 as compared with the less loaded gases of bulk powder, or 

 the unloaded gases of extraded or concentrated powder. 



The report is, therefore, heavier and more prolonged, 

 whilst the back pressure, which is another name for 

 recoil, is greater than with smokeless powder. 



7a 



