172 ANNUAL OF SCIENTIFIC DISCOVERY. 



present in the air. With gases differing so much in density and dif- 

 fusibility as oxygen and hydrogen, the separation is, of course, much 

 more considerable. The explosive mixture of two volumes of hvclro^en 



d 



and one volume of oxygen gave oxygen containing only 9.3 per cent, 

 of hydrogen, in which a taper burned without explosion ; and with 

 equal volumes of oxygen and hydrogen, the proportion of the latter 

 was easily reduced from 50 to 5 per cent. 



Speculative Ideas respecting the Constitution of Matter. It is con- 

 ceivable that the various kinds of matter, now recognized as different 



/ ^j 



elementary substances, may possess one and the same ultimate or 

 atomic molecule existing in different conditions of movement. 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 ascer- 

 tain that every kind of substance, " metals, stones, woods, grain, salts, 

 animal substances, etc.," are similarly accelerated in -falling, and are 

 therefore equally heavy. In the condition of gas, matter is deprived 

 of numerous and varying properties with which it appears invested 

 when in the form of a liquid or solid. The gas exhibits only a few 

 grand and simple features. These again may all be dependent upon 

 atomic and molecular mobility. Let us imagine one kind of substance 

 only to exist, ponderable 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 convertible into 

 heavy matter. In short, matter of different density forms different 

 substances, different inconvertible elements as they have been con- 

 sidered. 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 not therefore the molecules of which the 

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

 result. The gaseous molecule must itself be viewed as composed of a 

 group or system of the preceding inferior atoms, following, as a unit, 

 laws similar to those which regulate its constituent atoms. We have, 

 indeed, carried one step backward, and applied to the lower order of 

 atoms, ideas suggested by the gaseous molecule, as views derived from 

 the solar system are extended to the subordinate system of a planet 

 and its satellites. The advance of science may further require an in- 

 definite repetition of such steps of molecular division. The gaseous 

 molecule is, then, a reproduction of the inferior atom on a higher scale. 

 The molecule or system is reached which is affected by heat, the diffu- 

 sive molecule, of which the movement is the subject of observation and 

 measurement. The diffusive molecules are also to be supposed uniform 

 in weight, but to vary in velocity of movement, in correspondence with 

 their constituent atoms. Accordingly, the molecular volumes of differ- 



