Patent for a new method of working hydrated volatile refrigerating agents and a new refrigerator. This design "involve[s] the use of such highly volatile matters as are capable of hydration — as, for instance, ammonia, that being the refrigerating agent preferable to all others . . . [and] is a simplification in the mode of operation, and in apparatus which enables the employment of comparatively unskilled labor, the production of apparatus at comparatively low cost, and the working of the ammonia-gas at comparatively low pressure, thus obviating the dangers" (lines 13-24).