622 [June 18, 



With respect to the different states of gas, liquid, and solid, it may 

 be observed that there is no real incompatibility with each other in 

 these physical conditions. They are often found together in the 

 same substance. The liquid and the solid conditions supervene upon 

 the gaseous condition rather than supersede it. Gay-Lussac made 

 the remarkable observation that the vapours emitted by ice and water, 

 both at C., are of exactly equal tension. The passage from the 

 liquid to the solid state is not made apparent in the volatility of 

 water. The liquid and solid conditions do not appear as the extinc- 

 tion or suppression of the gaseous condition, but something super- 

 added to that condition. The three conditions (or constitutions) 

 probably always coexist in every liquid or solid substance, but one 

 predominates over the others. In the general properties of matter 

 we have, indeed, to include still further (1) the remarkable loss of 

 elasticity in vapours under great pressure, which is distinguished by 

 Mr. Faraday as the Caignard-Latour state, after the name of its dis- 

 coverer, and is now undergoing an investigation by Dr. Andrews, 

 which may be expected to throw much light upon its nature ; (2) 

 the colloidal condition or constitution, which intervenes between the 

 liquid and crystalline states, extending into both and affecting proba- 

 bly all kinds of solid and liquid matter in a greater or less degree. 

 The predominance of a certain physical state in a substance appears 

 to be a distinction of a kind with those distinctions recognized in 

 natural history as being produced by unequal development. Lique- 

 faction or solidification may therefore not involve the suppression of 

 either the atomic or the molecular movement, but only the restriction 

 of its range. The hypothesis of atomic movement has been elsewhere 

 assumed, irrespective of the gaseous condition, and is applied by Dr. 

 Williamson to the elucidation of a remarkable class of chemical re- 

 actions which have their seat in a mixed liquid. 



Lastly, molecular or diffusive mobility has an obvious bearing upon 

 the communication of heat to gases by contact with liquid or solid 

 surfaces. The impact of the gaseous molecule, upon a surface pos- 

 sessing a different temperature, appears to be the condition for the 

 transference of heat, or the heat movement, from one to the other. 

 The more rapid the molecular movement of the gas the more frequent 

 the contact, with consequent communication of heat. Hence, pro- 

 bably, the great cooling power of hydrogen gas as compared with air 



