ON ARTIFICIAL REFRIGERATION. 943 



tor as it passes tlirougli it. Tlie piston is caused to move in sncli a man- 

 ner tliat the air whilst being compressed will ahvaysbe at one end of the 

 vessel, and whilst being expanded be always at the opposite end of the 

 same, the regenerator preventing the conveyance of heat or cold by the 

 air from one end of the vessel to the other. The heat generated diu-ing 

 compression is removed by exposing that part of the vessel to a current 

 of cold air, water, or other cooling medium, whilst the cold produced at 

 the other end by expansion is used to refrigerate any liquid or substance 

 which may be brought in contact therewith. 



Mr. Kirk afterwards found an advantage in using damp air instead of 

 dry air, and in his paper on the Mechanical Production of Cold, read in 

 1874, before the Institute of Civil Engineers in London, he established 

 the following comparison : 

 In dry-air machine : 



Indicated horse-power, 7.08. 



Eejected heat = 1,409 pounds of water heated 1*^ Fahr, per minute. 



Absorbed heat, 1,100 pounds of water cooled 1° Fahr. per minute. 

 In wet-air machine : 



Indicated horse-power, 7.8. 



Eejected heat, 2,271.2 pounds of water heated 1° Fahr. per minute. 



Absorbed heat, 1,795.2 pounds of water cooled 1° Fahr. per minute. 



The professed improvements of Messrs. Windhansen, of Germany,, and 

 Paul GilTard, of Paris, relate to matters of detail of secondary impor- 

 tance, and it is well recognized now that where water-power can be had 

 and condensing- water is abundant, a cold-air machine may be used, but 

 it is much too cumbersome and wasteful for such imrposes as have re- 

 cently been suggested for ice-machines in steamers for the transport 

 of provisions or for sanitary puri^oses. 



Q— GAS ICE-MACHIXES OF NEW TYPE. 



The difficulties which I first encountered, with reference to the special 

 object for which I wanted to use artificial cold, were the unsuitable char- 

 acter of absorption (Carre) machines for ships' use ; the unwieldy and 

 power-absorbiug nature of air-machines; the exi)losive character of 

 ether-machines. 



In dealing with pump-machines such as the Harrison sulphuric-ether 

 and the Tellier methylic-ether apparatuses, the greatest objections I dis- 

 covered were, the explosive character of the materials, and the quantity 

 of these to be stored in a machine w^hich might leak and distribute a very 

 inflammable gas in a vessel, especially in hot latitudes, where even sul- 

 phuric ether is in the gaseous state at atmospheric pressure. 



M. Tellier has always spokenof the explosiveness of ether as of second- 

 ary imj)ortance, and has declared that it is needless discussing the ques- 

 tion when alcohols, essences, gases, petroleum oils, &c., are entrusted, to 

 ignorant people and children, under conditions when real danger might 

 be api)rchended. But two blacks do not make a white; and the binary 



