.v/A' WILLIAM SIEMENS, F.R.S. 317 



signifying that it was cast steel of a certain quality. He thought 

 there should be no practical difficulty in deciding which material 

 existed in a structure ; and with a material such as cast steel, 

 there would be, as he had stated, an available strength three times 

 greater than that of ordinary wrought iron, 



In the discussion of the Jty>rr 



"ON THE ARTIFICIAL PRODUCTION OF COLD," 

 By PROFESSOR JOHN GAMGEE, 



THE CHAIRMAN * (Mr. C. W. Siemens), in proposing a vote of 

 thanks to Professor Gamgee, said there was no doubt that the 

 machine described was theoretically the same as the ether machine ; 

 it was simply a question of the details of construction ; but some- 

 times these matters were of great practical importance in the 

 result. Mr. Reece's machine, on the other hand, was of an essen- 

 tially different character. He did not use mechanical force, but 

 produced the refrigerating action by the evaporation of water and 

 ammonia, and re-absorption of the ammonia by water. That, 

 no doubt, was a different conception of the same problem, but 

 finally it came to the same theoretical result, although the ammonia 

 machine avoided the losses connected with the steam-engine, which 

 were very considerable. It had been correctly stated that a ton of 

 fuel ought to produce something like 80 tons of ice, but consider- 

 ing that a considerable quantity of heat must always be wasted, from 

 40 to 50 tons was about the practical limit. He could not agree 

 with Mr. Hancock, that in hot climates the liquid to be employed 

 must be different, because the question of the liquid to be chosen 

 did not depend on the external temperature, but upon that which 

 you wanted to produce. In the case of Mr. Gamgee's machine, 

 the amount of compression that had to be performed by the pump 

 would be much less if the water were at 60, than if it were at 80* 



* Excerpt Journal of the Society of Arts, Vol. XIX. 1870-1871, p. 502. 



