CHAP, iv.] APPLICATIONS OF THE LAWS OF HEAT. 



385 



A is the boiler where the solution of ammonia is heated. The gas 

 which escapes from it is carried to the receiver, B, where it liquefies 

 by cooling, c is a reservoir out of which a jet of cold water con- 

 stantly runs to renew the water in the receiver. The liquefied gas 

 passes on to fill the hollowed sides of the refrigerator, G, where ves- 

 sels filled with the water to be frozen are placed. The water of 

 the boiler, deprived of its dissolved gas and cooled, then passes 

 into a vessel, E, which is in communication with D, and with 

 the refrigerator. The liquid ammonia resumes the gaseous state, to 

 dissolve again in the water in the vessel E, and it is by the cold 

 caused by this evaporation that the water freezes in the vessels 



FIG. 265. Carre's large apparatus for the artificial manufacture of ice. 



placed within the refrigerator. The water restored to its original 

 state again, is raised by a pump, F, to the boiler, so that the manufacture 

 of ice goes on in an almost continuous manner. 



We next give some further details on the artificial production of 

 ice based on the cold that results, not only from the brisk evaporation 

 of a liquid, but from the solution of certain substances. The cause is 

 still a change of state, but here it is a liquefication of a peculiar 

 kind, requiring molecular work, and, in consequence, absorbing a 



c c 



