316 Mr. F. /. Bramwell. [Feb. 27, 



jectile was moved further and further from the cartridge until an air 

 space of 10 feet was left. 



You will observe that the pressure, as indicated by the crusher 

 gauge, decreased as the space increased, so that with the 110-lb. charge 

 and the Palliser shell, instead of a pressure of 21*8 tons per square 

 inch when there was not any air space, there was a pressure of only 

 6 • 2 tons per square inch when that air space was increased to 10 feet, 

 and with the 85-lb. charge and the common shell instead of a pressure 

 of 20*2 when there was not any air space 1 * ton only was exerted 

 when the air space was increased to the 10 feet. 



The velocity of the shot and the recoil of the gun, it will also be 

 observed, diminished as the air spaces increased. 



These experiments entirely corroborated those which had been 

 made by Captain Noble prior to my last lecture. 



Although in the foregoing experiments with pebble powder 

 burning comparatively slowly, no excess of pressure was attained, 

 because the general diminution of pressure, owing to the enlarged 

 space the gases had for their expansion, more than compensated for 

 any increase due to ram action, yet it is perfectly possible by the use 

 of a small grain, or highly inflammable powder, to set up a local 

 pressure on the base of the shell precisely on the principle on which 

 a water ram acts, and precisely on the same principle as that in which 

 in the year 1870 I showed to the Institution of Mechanical Engineers 

 how steam might be caused to deliver a greater pressure than that 

 which prevailed in the boiler from which the steam came. 



The question arose in the following manner. The late M. Le 

 Chatelier had devised a mode of arresting railway trains without the 

 use of breaks, by means of that which has become known as the 

 " Centre Vapeur " system. This consisted in (as we engineers say) 

 putting the engine into "back gear," so that the pistons instead of being 

 propelled by the steam were converted into pump buckets forcing the 

 steam back into the boiler. You may say, as many did say, that 

 this amounted to nothing more than that which every engine driver 

 does as a last resource to avoid collision — reverse the engine ; but the 

 reversal of an engine while in rapid motion is with an ordinary 

 locomotive never resorted to except in dire necessity, because there is 

 great danger of scoring the cylinder and the piston-rod, and of burn- 

 ing the packing in the stuffing boxes. This arises from the rise of 

 temperature in the cylinders, due to the conversion of the stored-up 

 energy of the train into heat. Le Chatelier was aware of this diffi- 

 culty, and provided against it by admitting a small jet of water into 

 the cylinders ; this water was converted into steam, which, in common 

 with the steam that came from the boiler, was pumped back into it. 



The plan has had considerable use in France, but has never made 

 its way in this country. 



In the year 1869, however, Mr. Beattie, the then locomotive 

 engineer of the London and South- Western Kailway, fitted one of 

 their engines for the purpose of trial, and I had the oi)portunity of 



