914 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



Professor Giitlirie lias not succeeded in getting tlie cryoliydrates of 

 glycerine. As a cryogen, the glycerine behaves as hydrochloric acid 

 and other liquid elements of cryogens, namely, the temperature obtained 

 is lower if the liquid be previously cooled. 



K.— CEYOGEX-MACHmES. 



Under this name may be included any apparatus calculated to facilitate 

 and bring about the regular admixture of water and a cryogen, the low 

 temperature produced being utilized to make ice, freeze creams, &c. The 

 only i)ractical domestic machines are really of this kind, and to what ex- 

 tent they may hereafter render good service in households and some indus- 

 tries, especially in hot climates, depends much on the careful apphcation 

 of the knowledge acquired by Professor Guthrie and his followers. Many 

 of the salts available for this i:>urpose are remarkable for thek stability, 

 and may be used for an indefinite i^eriod of time. The cost of the evap- 

 oration of water will determine the cost of the resulting cold, and the 

 sun's heat may enable, the jiarched residents of tropical countries, to 

 enjoy the comfort and luxury of very economical methods of artificial 

 refrigeration. 



In relation to fish-culture, the transportation of ova on steamers, and 

 for securing definite and unvarying temperatures at small cost, in mod> 

 erate compass, the cryogen-machine offers many advantages. At sea, 

 exhaust steam may be had in any quantity to dry the salt. The time 

 required to dry the salt, the amount of material to he cooled, and the 

 mechanical facilities for the alternate liquefaction and solidification of 

 the salt are matters of great practical moment which have received but 

 little attention hitherto. In this direction we must anticipate a great 

 revolution in artificial refrigeration, especially as applied to the subjects 

 most immediately under consideration in this paper. I need, therefore, 

 make no excuse for reproducing the following table, showing (1) the 

 chemical formula of the salt, (2) the lowest temperature to be got by 

 mixing the salt with ice, (3) temi)erature of solidification of the cryohy- 

 drate, (4) molecular ratio between anhydrous salt and water of its cryo- 

 hj'drate (water- worth or aquavalent), (5) percentage of anhydrous salt 

 in portions of cryohydrate last to solidily, (6) percentage of anhydrous 

 :salt in crop of cryohydrate before the last. 



