Atomic Constitution of Elastic Fluids. 37 



It has been the object of the foregoing remarks to prove 

 that there does not exist, in the principles of general physics, 

 any foundation for the new doctrine of Dr. Prout and M. Du- 

 mas, " that a given volume contains the same number of ulti- 

 mate atoms in all the different gases*." These principles, 

 however, with the exception of the relations of specific heats, 

 though they do not furnish any support to such a doctrine, 

 must be acknowledged to involve nothing that is contradic- 

 tory to it. It must be considered, therefore, simply as an 

 hypothesis, the value of which is to be estimated by its appli- 

 cability to chemical phenomena. When tried by this test, it 

 will be found wholly untenable, unless it be supported by a 

 second and yet more improbable hypothesis, " the divisibility 

 of the atom." Indeed, the single example of muriatic acid 

 gas is sufficient to demonstrate its unsoundness. A volume 

 of this gas is constituted of half a volume of hydrogen and 

 half a volume of chlorine. The number of atoms in a volume 

 of hydrogen is therefore double that in the same volume of 

 muriatic acid gas. Nitrous gas, in like manner, must contain 

 half the number of atoms that are contained in an equal volume 

 of azote. The same is true of ammoniacal gas, of hydriodic 

 acid gas, of hydrocyanic and chlorocyanic acid vapours, and 

 of the vapour of sulphuret of carbon, when compared with an 

 equal volume of one of their constituents. It may, then, be 

 confidently asserted, that chemical phsenomena, at least as 

 they are now generally interpreted, are inconsistent with the 

 notion of an equality of atoms in all gases, compound and 

 simple. 



It is solely upon this supposed numerical equality of atoms 

 that Dr. Prout's second proposition is founded. Now if it has 

 been shown that such equality is not derivable from physical 

 principles, and is also inconsistent with known chemical facts, 

 that proposition can be no longer maintained, except as an in- 

 dependent hypothesis; and we are compelled, by the rules of 

 philosophizing, to recur to the simple and beautiful concep- 

 tion of the indivisibility of the atom, taught by the illustrious 

 author of the atomic system. Several considerations may, 

 moreover, be urged in favour of the doctrine of Dalton, that 

 the mutually repulsive molecules of elastic fluids are identical 



* It is not asserted that there do not exist any two gases which contain 

 in the same volume the same number of ultimate atoms. On the contrary, 

 most of the simple gases and vapours, and some of the compound gases, 

 are generally believed to be thus similarly constituted. We object only to 

 the raising what is true in certain individual examples into a general and 

 necessary proposition. 



