1821.] Remarks upon Mr. Her apalh's Theory. 225 



gases to be in contact, then the particles which form the surface 

 of each, will, by their repulsive force, endeavour to fly off from 

 the masses to which they respectively belong ; and they will fly 

 off among the particles of the other gas, there being nothing to 

 prevent them, till they reach the surface of the containing ves- 

 sel ; and this being the case with both gases, they must neces- 

 sarily mix throughout the whole space which contains them. 



Of the theorem given in p. 403, our author has not given us the 

 least clue to a demonstration. In the Annals for July, 1816, it 

 is given as a cor. to a more general theorem, which, I own, 

 appears to me involved in an inconsistency. According to 

 Prop. VIII. elasticity varies as the numeratom x square of 

 temp. By this theorem it is as the square of temp, x the 

 square of the numeratom, and inversely as the specific gravity. 



The inference which he makes from hence respecting the 

 composition of water appears to be directly at variance with the 

 clear result of all experiments. Yet Mr. H. admits that either 

 may be true, or neither, but maintains that it is beyond our 

 power to demonstrate which is the case. The established 

 doctrine upon this point is surely demonstrated to be the true 

 one, if any ever was. He alludes to the subject in his paper 

 published in 1816 ; and there says, that the common theory 

 takes for granted that equal volumes of any two gases, ceeteris 

 paribus, contain an equal number of particles. But 1 beg to 

 suggest whether this supposition is at all made. We find by 

 experiment that the proportion of 2 hydrogen to 1 oxygen holds 

 good whatever be the volumes we try, and thence we clearly 

 and rightly infer, that the same must also be the case when the 

 volumes are infinitely small, or atoms ; but it is admitted that the 

 atom of oxygen is of greater weight or density, and, therefore, 

 contains more matter. Thus Mr. H.'s view of the subject may 



Eossibly not be inconsistent with the atomic theory. Though 

 is definition of atoms is not easy to be conceived (see Annals, 

 July, 1816), I would propose to his further consideration one 

 difficulty attending it. Some atoms, he admits, may be com- 

 posed of smaller particles; and, therefore, there can be no 

 repulsions or collisions among these particles, yet there is be- 

 tween the u little individual bodies " formed by them, and the 

 other atoms of the gas ; and as they must all be of the same 

 kind, and endued with the same properties, there is a difficulty 

 in conceiving how some of them come to unite, and others to 

 repel one another, which needs some explanation. 



The. theorem which he gives for the temperature of a mixture 

 in p. 403 is left without explanation ; and as the results derived 

 from it agree nearly with those from other sources, there is of 

 course very little evidence gained in favour of either theory. 

 But the theorem in question rests upon the existence of a point 

 of absolute cold ; and, therefore, we must hesitate in admitting 

 it till we have made up our minds on that much controverted 

 New Series, vol. ii. q 



