Chambers's Edinburgh Journal, No. 430

he thermometer and dry to the hygrometer; or, in other words, dense, and containing little else than the necessary oxygen and azote, and this supplied to a room, fresh and fresh, in a continual current.'

He next goes on to describe the principle of his new plan of cooling:--'The method by which I propose to accomplish this consummation, so devoutly to be desired, is chiefly by taking advantage of the well-known property of air to rise in temperature on compression, and to fall on expansion. If air of any temperature, high or low, be compressed with a certain force, the temperature will rise above what it was before, in a degree proportioned to the compression. If the air be allowed immediately to escape from under the pressure, it will recover its original temperature, because the fall in heat, on air expanding from a certain pressure, is equal to the rise on its being compressed to the same; but if, _while the air is in its compressed state, it be robbed of its acquired heat of compression_, and then