Plainly, the power of producing liquid air opens to applied science new horizons. There is no need to prove that, from the purely scientific and philosophical point of view, M. Cailletet's experiments are of supreme importance.
We will conclude this article with a description of the little lecture-room or laboratory apparatus, constructed by M. Ducretet, to show how, according to Cailletet's process, gases are liquefied. It is a copy of the essential parts of the apparatus at Châtillon-sur-Seine. The bell-glass is modified. The screw-press, too, is represented here by a more portable pump. The accompanying figure, which
represents the apparatus in section, will enable us to give a more detailed description of the system devised by M. Cailletet.
T T is a glass tube, containing the gas to be compressed; a cur-