Dr. E. J. Mills av die Atomic Theory. 117 



fact, only one succhiif and one pyrotartaric acid are at present 



jviTtTvVIT. 



" If, on the other hand, bromine be put in those same unoc- 

 cupied spaces, the carbon within the molecule is partly united 

 with hydrogen, partly with bromine ; and it is readily perceived 

 that different modifications of such bromo-acids must necessarily 

 exist, according as the bromine finds itself in one or the other of 

 those spaces." 



This mode of explanation is now virtually common to all 

 atomic theorists. It is assumed that substances consist of mole- 

 cules, these again of atoms ; that determinate space or position 

 (Stelle) is conceivable without atoms, and exists indeed in their 

 absence ; and that into this space there stretch at all times mys^ 

 terious units of affinity, which, when the atoms are no longer 

 present, strive after combination. But if all chemical substances 

 consist of atoms, and position is possible without them, how can 

 such position be known or determined ? According to Hegel, 

 pure being is pure nothing ; and we may assign pure position to 

 the same category. But determinate space or position, with the 

 only thing that can determine it taken away, is contradiction 

 itself. Still more unsatisfactory are the units of affinity (Ver- 

 wandtchaftseinheiten) . They cannot be chemical substance, or 

 they would be identical with the atom ; they cannot be dyna- 

 mical units, similar to foot-pounds, for no such integral relations 

 as they would then present have been found in the measurements 

 of chemical action. Yet unquestionably dynamical language is 

 used of them ; they are said " to make an effort/'' " to bind on," 

 "to rivet together," &c. It is much to be deplored that no 

 atomic theorist has yet thrown light on the obscure question of 

 units of affinity, or even stated in clear terms what he means by 

 them. In the absence of any such statement, I shall class them, 

 as pure number, in the roomy category of Hegel. 



If any one were to observe under a microscope a small insect 

 with cephalic, thoracic, and abdominal appendages, and were 

 afterwards to assert that these were six in number, there being- 

 two of each name — that he had removed two of them, which the 

 insect made a proportionate effort to reunite to its body, and 

 that as the remaining four were removed an increased struggle 

 was manifest — such statements, I say, would be conceivably 

 true. But when language like this is used to explain to me the 

 " structure " of a succinate, I decline to accept either its sub- 

 stance or its form, until the facts alleged of the succinate are 

 put upon the same footing as those asserted of the insect. Until 

 then, " units of affinity " may be considered as false an expres- 

 sion as " units of hunger " would be now. 



Kekule himself, by admitting a class of isomers " im engeren 



