176 HISTORY OF CHEMISTRY. [LECTURE X. 



than either Dalton or Berzelius had considered possible, and 

 the law had, on this account, obviously to some extent lost its 

 definite character. Even at that time the question might have 

 been asked, whether the statement could be called a law, since 

 chemists were not in a position to determine anything as to the 

 limits of the power of combination of atoms ; and also whether 

 every compound could ultimately be referred to unvarying 

 weights of the constituents, if any large multiple might be 

 chosen at will. Ideas of this kind do not appear, however, to 

 have arisen at that period, 5 and so there always remained this one 

 generalisation for those who tried to retain the atomic theory and 

 to advance speculations as to the constitution of compounds. 

 Amongst these, Dumas had in the recent years played the most 

 important part, by founding his theory of types. In this theory, 

 which was, no doubt, partly borrowed from Laurent, there was 

 much that was eminently suited for a classification of organic 

 compounds ; but still the use of it was only recognised more 

 generally after its fusion with the radical theory, that is, after 

 radicals had been introduced into the types. This could only 

 take place after the conception of the radical had been com- 

 pletely transformed, and it is now my business to show how 

 and by whom this development was brought about. 



On studying the writings of the founders of the radical 

 theory, one might be tempted to assert that it was they who 

 not only established the conception of the radical in its first 

 signification, but that, at the same time, they had also done 

 the most important service in respect of the subsequent 

 acceptation of the word. Thus, the following passage from 

 Berzelius is noteworthy : 6 



"We shall assume that, by means of any circumstance 

 whatsoever, we could clearly see the relative position of the 

 simple atoms in the compound atom of the salt [sulphate of 

 copper]. It is clear that, whatever this may be, we should 

 then find in it neither oxide of copper nor sulphuric acid, for 



5 Compare, however, Berzelius in Liebig's Annalen. 31, 17 ; also 

 Dumas, ibid. 44, 66. 6 Jahresbericht 1835, 348. 



