^ 



122 Mr. A. Tribe's Remarks on the Atomic llieory. 



which those elements at present known follow each other/^ 

 and that^ ^'' to explain Dulong and Petit's law^ the assumption 

 must be made that the effect of a given quantity of heat in rai- 

 sing the temperature of a solid mass containing a given number 

 of elementary atoms all of the same kind is independent of the 

 nature of the atoms/'' Dr. Wright has collected a number of 

 facts on whichL the philosophy of chemistry is based ; and his 

 essay is useful en that account \ but the analysis of these charges 

 of insufficiency demonstrate tliat^ in his zeal, he lost sight of the 

 aim of the theory, and endeavoured to make it answerable for 

 phenomena with which it has no necessary connexion. These 

 "remarkable approximate relationships^^ and this "remarkable 

 sequence ^^ are facts of some small interest. It is, however, no 

 more the part of the atomic theory even to suggest their cause, 

 than it is to explain why atoms of different substances differ 

 in weight, or why chlorine and bromine, possessing, as they do, 

 so many chemical analogies, should be respectively a yellowish- 

 green gas and a reddish-brown liquid. 



Dulong and Petif's law is the expression of a really remark- 

 able series of experimental facts, and has been instrumental in 

 no small degree in increasing the faith in the existence of atoms. 

 But why this argument against the idea of the atomic constitu- 

 tion of matter because quantities of certain elementary bodies 

 expressed by their atomic weights require the same amount of 

 heat to raise them to a given temperature, I am at a loss to un- 

 derstand. Had more than a superficial view of this subject been 

 taken, the discovery would have been made that it is the 

 atomic theory which welds Dulong and Petit^s results into a 

 law — that, in fact, the law exists in virtue of the theory, and con- 

 sequently that the theory is independent of the law. Even were 

 it a fact that atomic proportions of the sixty-four known elemen- 

 tary bodies required as many different amounts of heat to raise 

 them to a given temperature, the fact could not be employed as 

 an argument for or against the atomic theory. 



If theories are to be charged with being insufficient on grounds 

 no more potent than have been brought against the atomic 

 theory, the theory of gravitation may fairly be expected to be 

 charged, at no distant day, with insufficiency because it gives no 

 clue to the cause of sun-spots or the physical constitution of the 

 sun ; the undulatory theory, because it gives no explanation of 

 the disinfecting action of burning brimstone ; and the theory of 

 the dissipation of energy, because it fails to account in a satis- 

 factory manner for the odour peculiar to Sauerkraut. 



Unnecessoriness. — Dr. Wright remarks, " some minds are un- 

 able to grasp the notion that, for example, 6 and 8 are 14 with- 

 out gomg through the mechanical process of counting on the 



