LIQUID AIR AS A MOTIVE POWER.
UNTIL liquid air has been rendered less perishable, and until it can be produced more economically than at present, it is not likely to come into use as a power-producing medium. Weight for weight, coal will produce twenty times as great an amount of power, and in durability is infinitely the superior of the newer power-producer. One pound of coal will evaporate ten pounds of water. As the latter is being converted into steam, it willexpand into about 1,700 times its volume as water, whereas ten pounds of liquid air will expand to only 800 times the volume as liquid (under an increase of temperature up to sixty-five degrees Falir.) To obtain the samepower as would be yielded by one pound ol coal would, therefore, take twenty pounds of liquid air. Wherefore, for the latter to compete with the former in cost it must be produced for the same money. But this is an impossibility, since liquid air costs nearly three dollars a pound, and cannot be stored or carried about, as can coal, indefinitely, without rapid deterioration. For instance, while a pound of ice wrapped in a blanket will last all night without being very much reduced in weight, the same weight of liquid air put in a can, wrapped in a blanket, and stowed away in a refrigerator, would disappear in a very few minutes, while the weight of a pound of coal would not be diminished in the least, even if carried from China to Peru, or from pole to pole and back again for generations. So also, a pound of ice, costing— say, one cent or two—will cool a refrigerator more than a pound of liquid air at a far higher price. Liquid air, therefore, need not at present be feared as a rival by any of those who deal in whatever kind of motive power that is in vogue today.