120 Mr. R. W. Atkinson on the Atomic Theory. 



that his exception of oxygen and chlorine on account of difference 

 of physical condition was referred to. In a note he objects to 

 my taking the specific heat of the gases under constant volume 

 instead of under constant pressure ; but that, I maintain,, is the 

 correct number to take, inasmuch as the excess of heat in the 

 latter case is only used in lifting the atmosphere through a cer- 

 tain space. 



Dr. Wright says that boron and carbon were not mentioned in 

 connexion with the rule; but why are two elements of such im- 

 portance to be neglected ? Does he, then, throv/ on one side every 

 thing which does not happen to coincide with his views ? 



It is not worth while discussing Dr. Wright^s repetition of 

 the statement that valency is a function of symbols; valency 

 being a property possessed by matter, cannot be merely a func- 

 tion of certain symbols. 



Instead of accounting for the differences between isomeric 

 bodies, Dr. Wright evades this by making a furious attack upon 

 the atomic theory respecting the validity of its own explanation. 

 All that his argument amounts to, however, is this, that the 

 relation between the motion of the atoms and the mechanical 

 properties of a body has not been studied. Until this is the case 

 it is absurd to expect the atomic theory to state what difference 

 in the motion of the atoms corresponds to a difference in the 

 mechanical properties of a body. The reactions of ethylic alcohol 

 and methylic ether are satisfactorily explained on the supposition 

 that in the first case an atom of oxygen binds together an atom 

 of ethyle and an atom of hydrogen, and in the second case it 

 binds together two atoms of methyle ; but any connexion be- 

 tween the motion of the atoms and the mechanical properties of 

 bodies must be left for future researches to point out. It is no 

 argument against the atomic theory to say that it does not ac- 

 count for certain properties, when it has never been apphed 

 to their explanation. It will be time enough to cry out 

 against it when it is found perfectly incompetent to do so after 

 the requisite knowledge has been obtained. But if that expla- 

 nation be rejected on account of its alleged insufficiency, what is 

 to take its place ? for it is evident, from the care with which he 

 evades the question proposed, that Dr. Wright has none to offer. 



University College Laboratoiy^ 

 July K3, 1872. 



