796 THE POPULAR SCIENCE MONTHLY, 



DU MOTAY'S PEOCESS OF ICE-MAKIE^G. 



Br G. B. SEELY. 



OF all the projects that have excited the ridicule of the unimagina- 

 tive of times gone by, perhaps none has appeared more exceed- 

 ingly funny and chimerical than that of producing at will, by mech- 

 anism operated by heat, a freezing cold, and that without the use 

 of ice, or any previously congealed substance, and without regard to 

 atmospheric temperature. 



In these days of rapid development of the mechanic arts, it seems 

 hazardous to assert impossibility of any mechanical problem involv- 

 ing the substantial amelioration of man's condition. The manifest 

 need of an improvement seems to be but the condition of its realiza- 

 tion and development ; sooner or later appears the embryo invention 

 destined to be the theme of long study and continual modification, the 

 perfected product often bearing little or no resemblance to the crude 

 prototype that may have first embodied an idea fraught with lasting 

 good to man. The conception once concretely realized, its beneficent 

 results become a part of the common capital of the race, making pos- 

 sible still further advances in our material well-being. 



While the progenitors of the race seem early to have discovered 

 the means of producing heat artificially, for their rude arts and for 

 their bodily comfort, it is not probable that the means of obtaining 

 artificial cold could ever have seemed to primitive man a pressing 

 need. Civilization is a multiplying of needs, and nothing connected 

 with man's development seems more clear than that the adoption of 

 artificial protection from the elements, conducing directly as it has to 

 a material modification of Nature's means of protecting the body and 

 providing for its wants, has not only led to the demand for readily 

 available means of producing artificial heat, but for the means of arti- 

 ficial refrigeration as well. 



Since the experiments of Professor Twining thirty years ago, with 

 sulphuric ether, the problem of producing artificial cold has been 

 attacked by many, but the basis of the more important and successful 

 systems employed has been, as in Twining's experiments, the volatili- 

 zation of a liquid in vacuo, by means of a gas-pump. Of the various 

 substances available in nature for this purpose, ether and ammonia 

 have received the most attention. Various other liquids have also 

 been used, such as sulphide of carbon, me thy lie ether, chloride of 

 methyl, chymogene, etc., and latterly sulphurous acid as used in the 

 famous Pictet system. Compressed air has also been employed, but 

 the mechanical labor required by this system is too costly to allow it 

 to compete with what may be termed the volatilizing systems. 



The object sought has been the most economical method of em- 



