Solids and Liquids at High Temperatures

Abstract

SOME years ago I made an investigation much simpler but somewhat similar to that referred to by Prof. Carnelley in NATURE, vol. xxii. p. 435. An account of the experiments then made was communicated to the Royal Scottish Society of Arts, 1874–75. One of the results of that investigation was that while we do know something about the temperatures at which different forms of matter change from one state to another when a “free surface” is present, yet we are utterly ignorant of the temperature at which that change will take place when no “free surface” is present. It will be necessary here to explain that a “free surface” is any surface of the body under examination at which it is free to change its state. A surface of water, for instance, in contact with its own vapour is a “free surface” for the water passing into the gaseous state. The surface of a piece of ice in water, again, is a “free surface” at which the water may freeze or the ice may melt. And what are known as the freezing, melting, and boiling points of water are the temperatures at which these changes take place when such “free surface” are present. As to what the freezing, melting, and boiling points are when these “free surface” are absent, we have at present no knowledge whatever. All we know is that the freezing point is lower, and the “melting” and “boiling points” are higher, than when “free surface” are present.