spreads out on the metallic surface, and is instantly thrown into violent ebullition. This striking phenomenon is generally known as Leidenfrost's experiment.
All volatizable liquids under similar circumstances behave as water does. Liquid sulphurous acid, for instance, when poured into a red-hot silver or platinum crucible, retains its spheroidal state; its temperature never rising beyond its boiling point. Now, as the boiling point of this liquid is 18°, and therefore much below the freezing point of water, we can actually freeze water in a red-hot crucible by pouring it into the sulphurous acid! The same thing occurs with a mixture of ether and solid carbonic acid when introduced into a red-hot metallic vessel. The mixture requires for its conversion into gas as much time as it would in the air at the ordinary temperature. If we introduce into this mixture a small tube containing a little mercury, the liquid metal instantly congeals into a solid! Again, in the place of a metallic basin or crucible, water near its boiling point may be made use of to support a drop of ether. Instead of mixing with the hot water, the ether gathers itself up into a globule and rolls about upon the surface of the other liquid.
Let us confine our attention to the original experiment, to the dancing drop in the red-hot basin. By a series of beautiful experiments it has been