BRITISH ASSOCIATION. 45 



know her strength — at a distance of 18 feet, and that not vertically, but laterally, 

 the question arose whether they might not fortify and protect those channel ways 

 by placing a ring of gun cotton magazines along the bottom ; but, at any rate, if 

 that was not necessary, they could float them at any depth, and out of reach of 

 the vessels generally u?ing the channel. That appeared to him to be one of the 

 most important uses of gun cotton, and it was one which would give safety to 

 cities which were some distance from the mouths of navigable rivers. He trusted 

 that in the event of the Committee continuing their labours, they would address 

 their attention to this important point. — Admiral Sir E. BELOHEa stated that the 

 explosion of powder under water was once done under ene of his own vessels to 

 clear away ice. He placed it upon the ground, thinking that its explosion would 

 blow the ice clear of her bows without touching the vessel. There was, however, 

 sufl&cient water to form a cushion, and when the explosion took place it only pro 

 dueed a great wave upon which the vessel rose. Prof. Pole said what they 

 wanted was something to show the varying pressure of the gases in the gun ; in 

 fact, an indicator diagram . — Mr. J. Soott Russell set himself to clear away the 

 many difficulties which attended this very difficult subject. How was it that in 

 gunpowder and in gun-cotton where there were equal quantities of gas put in, the 

 gas in the case of gunpowder was raised to an enormously high temperature, and 

 came out at an enormously high pressure, showing that they had gas enormously 

 expanded by heat; whereas in the case of gun-cotton the gas came out quite cool, 

 so that you might put your hand upon it, and the gun itself was quite cool ? He 

 (Mr. Russell) had a theory. Steam was a gas, and steam expanded just by the 

 same laws as other gases did. A great deal of the gas of gun-cotton happened to 

 be steam. Let them conceive 100 lb. of gun-cotton shut up in a chamber that just 

 held it. They had got there all the gases that had been spoken of, but they had 

 also got 25 lb. of solid water — about one- third of a cubic foot of water — in that 

 chamber. What did they do with it? They put fuel, they put fire to it. They 

 heated the whole remaining pounds of patent fuel. If, then, they considered the 

 gun-cotton gun as the steam-gun, they got rid of two difficulties. They would 

 have, first, the enormous elasticity of steam ; and secondly, they would get the 

 Coolness of it. They all knew that if they put their hand to expanded high pres- 

 sure steam, it had swallowed up all the heat and came out quite cool. He believed 

 that the gun cott n gun was neither more nor less than Perkins's old steam gun 

 with only this difference, that you bottled up the fuel and water, and let them 

 fight it out with each other. They did their work and came out quite cool. He 

 hoped, however, that it was understood that he did not dogmatize. He put all he 

 had said with a note of interrogation upon it. Prof. Ttndall said he thought that 

 a note of interrogation ou^ht to be put to what Mr. Russel had said. 



The subject is considered of so much importance that the British Association, 

 though it has re-appointed the Joint-Committe to continue its inquiries, has 

 passed a resolution to urge on the Government the appointment of a Commission 

 by means of which a more complete investigation, and such as the subject unques- 

 tionably deserves, may be made than the means at the disposal of the Association 

 will admit of. 



