ICE, ARTIFICIAL

the production of ice through various chemical or mechanical means. As an industry the artificial production of ice only became important in about 1880, but fifty years before that machines had been perfected which could produce it, though not cheaply enough:to make them a commercial succe . Prof. A, C. Twining, of New Haven, Conn., was one of the most prominent inventors in this line of effort, in the early fifties. Such machines require steam power to work them, and their action consists in evaporating pure ammonia in a vacuum, and again condensing the vapor to a liquid, so as to be used afresh. By such machines 20° F. below zero has been easily obtained. By the modern method pure ammonia is brought to the boiling point by the pre ure of a steam pump. After it is transformed into a gas. it pa es into cooling pipes, where it condenses, thus producing cold artificially. These pipes pa about the tanks containing the water to be frozen. The number of methods and their variations. may be judged by the fact that over 3,000 patents have been i ued on ice mach in- | ery. There are about 3,000 ice plants in the United States, most of them in the South, where natural ice is not easily procurable, and in large cities in the North, such as New York, where the demand is large. The use of artificial ice is gradually spreading Northward, however, the lowering of the cost’ of ‘production rendering it 4 stronger competitor of natural ice.