620 [June 18, 



taking the direction of the hydrogen and carrying back in mass a 

 little air, or the slower gas, whatever it may be. I cannot account 

 otherwise for the slight predominance which the lighter and faster 

 gas appears always to acquire in diffusing through the porous septum. 



Speculative ideas respecting the constitution of matter. 



It is conceivable that the various kinds of matter, now recognized 

 as different elementary substances, may possess one and the same 

 ultimate or atomic molecule existing in different conditions of move- 

 ment. The essential unity of matter is an hypothesis in harmony 

 with the equal action of gravity upon all bodies. We know the 

 anxiety with which this point was investigated by Newton, and the 

 care he took to ascertain that every kind of substance, "metals, 

 stones, woods, grain, salts, animal substances, &c.," are similarly 

 accelerated in falling, and are therefore equally heavy. 



In the condition of gas, matter is deprived of numerous and vary- 

 ing properties with which it appears invested when in the form of a 

 liquid or solid. The gas exhibits only a few grand and simple fea- 

 tures. These again may all be dependent upon atomic and molecular 

 mobility. Let us imagine one kind of substance only to exist, pon- 

 derable matter ; and further, that matter is divisible into ultimate 

 atoms, uniform in size and weight. We shall have one substance 

 and a common atom. With the atom at rest the uniformity of 

 matter would be perfect. But the atom possesses always more or 

 less motion, due, it must be assumed, to a primordial impulse. This 

 motion gives rise to volume. The more rapid the movement the 

 greater the space occupied by the atom, somewhat as the orbit of a 

 planet widens with the degree of projectile velocity. Matter is thus 

 made to differ only in being lighter or denser matter. The specific 

 motion of an atom being inalienable, light matter is no longer con- 

 vertible into heavy matter. In short, matter of different density 

 forms different substances different inconvertible elements as they 

 have been considered. 



What has already been said is not meant to apply to the gaseous 

 volumes which we have occasion to measure and practically deal 

 with, but to a lower order of molecules or atoms. The combining 

 atoms hitherto spoken of are therefore not the molecules of which 

 the movement is sensibly affected by heat, with gaseous expansion as 



