970 EEPORT OF COMMISSIONER OF FISH AND FISHERIES. 



and this at ouce indicates tlie wide application of an entirely new system 

 of supplying- conmuuiities with pm^e water, where under existing- cir- 

 cumstances none can be had. 



Professor Baml, in the letter requesting me to furnish information at 

 my disposal on the manufacture of ice and the preservation of fish, has 

 directed my special attention to the dearth of water in places on the sea- 

 coast, such as Gloucester, Mass. This opens up a ^ide field of opera- 

 tions wherever ice-machines are estabUshed for the use of fisheries; and 

 without attempting to determine the extent and actual form of appli- 

 ances required in practice, the data at our disposal indicate tlie feasi- 

 bility of making ice from sea- water and supplying a to^\Ti with drinking- 

 water of great purity. 



M. TeUier, having described the congealer in his 18G9 patent, goes on 

 to say that another application, hitherto vainly attempted, is the prep- 

 aration of fresh Avater at sea by means of congelation. It is a well-known 

 fact that the water of the sea, when congealed, casts off the salts which 

 it holds in solution, and that water is thus obtained quite as fresh as 

 that produced by distillation, with this difference, however, in favor of 

 the congealing process, that while a glass of distilled water can hardly 

 be swallowed, there is no pleasanter drink than melted ice. Let the con- 

 gealer be filled with sea- water, allow sufiBcient time for congelation to 

 take place, and then run out the liquor laden Avith salts; the fresh water, 

 in the shape of ice, will remain in the apparatus. This ice, being aUowed 

 to melt, will furnish, either alone or mixed with tlistilled or other water, 

 excellent drinking-water, fit for any purpose. 



Messrs. Henri Merle & Co., at Giraud, on the Mediterranean coast of 

 Prance, adopted M. Carre's ammonia-machines soon after they were first 

 constructed, at their salines, covering 25,000 acres.* Pour-fifths of the 

 chloride of sodium is removed from the sea-water by solar heat. A mix- 

 ture of sulphate of magnesia and chlorides of magnesium and potassium 

 remains in the mother-water, and this, on being subjected to — 18° C, or 

 a little below 0° Fahr., yields, by a double decomposition of common 

 salt and sulphate of magnesia, sulphate of soda, which deposits in crys- 

 tals, and a solution of magnesium chloride. The sulphate of magnesia 

 is almost entirely withdrawn from the water, and the sulphate of soda 

 which is obtained is a valuable commercial product, being the material 

 from which carbonate of soda is prepared. The waters are now subjected 

 to evaporation over the fire, and the remaining common salt which they 

 contain is deposited in the form of the most beautiful fijie salt. The 

 chlorides of magnesium and potassium still remain in solution; but when 

 the concentration has reached the specific gravity 1.31, the solution is 

 allowed to flow over a broad surface of concrete (bcton), where, in cool- 

 ing, it parts with all the potash it contains in the form of a double chlo- 

 ride of potash and magnesium. The remaining water, containing only 

 chloride of magnesium, is rejected. This waste salt may hereafter prove 

 ofgreat value as a cryogen, and I have used its watery solution exten 



* General Survey of the Paris Universal Exhibition, 18G7. Wasliingtou, 1868. 



