the Constitution of Matter. 8$ 



late. A special rate of vibration or pulsation originally im- 

 parted to a portion of the fluid medium enlivens that portion of 

 matter with an individual existence, and constitutes it a distinct 

 substance or element. 



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 super- 

 vene upon the gaseous condition rather than supersede it. Gay- 

 Lussac made the remarkable observation that the vapours emitted 

 by ice and water, both at 0° C, are of exactly equal tension. 

 The passage from the liquid to the solid state is not made appa- 

 rent in the volatility of water. The liquid and solid conditions 

 do not appear as the extinction or suppression of the gaseous 

 condition, but something superadded 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 discoverer, and 

 is now undergoing an investigation by Dr. Andrews, which may 

 be expected to throw much light upon its nature ; (2) the col- 

 loidal condition or constitution, which intervenes between the 

 liquid and crystalline states, extending into both and affecting 

 probably all kinds of solid and liquid matter in a greater or less 

 degree. The predominance of a certain physical state in a sub- 

 stance appears to be a distinction of a kind with those distinc- 

 tions recognized in natural history as being produced by unequal 

 development. Liquefaction or solidification, therefore, may not 

 involve the suppression of either the atomic or the molecular 

 movement, but only the restriction of its range. The hypo- 

 thesis of atomic movement has been elsewhere assumed, irre- 

 spective of the gaseous condition, and is applied by Dr. William- 

 son to the elucidation of a remarkable class of chemical reactions 

 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 possessing 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 move- 

 ment of the gas, the more frequent the contact, with consequent 

 communication of heat. Hence, probably, the great cooling - 

 power of hydrogen gas as compared with air or oxygen. The 

 gases named have the same specific heat for equal volumes ; but 



G2 



