110 HISTORY OF CHEMISTRY. [LECTURE VII. 



between its supporters, with Berzelius at their head, and the 

 adherents of the substitution theory or the theory of types. 

 This controversy was triumphantly passed through by the latter, 

 and led to the complete separation of organic and inorganic 

 chemistry. At any rate the endeavour was still made to retain 

 in the latter, as before, the dependence of the chemical upon 

 the electrical forces, whilst the newest facts in the domain of 

 organic chemistry appeared to be incompatible with this. Our 

 science thus fell anew into two schools, and the principles which 

 guided the one school were rejected by the other. 



Simultaneously with the abandonment of the electro- 

 chemical hypothesis, the radical theory was also given up ; 

 there was now no longer any actual need for it, and, in the 

 form in which it had been advanced, it was insufficient. A 

 great deal had been discarded as useless, and therefore it is by 

 no means inadvisable to inquire into the principles which still 

 remained with the representatives of the new school. The 

 views as to the preservation of the type, and as to substitution, 

 although, of course, most valuable for the comprehension of 

 many reactions, could scarcely be employed as the basis of a 

 complete system. But amongst the ruins left upon the battle- 

 field, and found there when it was cleared up, there was a 

 jewel, which, although little heeded during the controversy, 

 was now capable of becoming of great significance when the 

 question was no longer one of getting rid of old views, but one 

 of setting up new views in their stead. The atomic theory, 

 despised by many, forgotten by some, was now destined to 

 arise again in its original brilliancy, although a hard struggle 

 was necessary. New foundations for the determination of the 

 relative masses of the atoms had to be obtained. It was 

 Gerhardt, in particular, who insisted on the necessity of fixing 

 upon comparable quantities for these determinations. But 

 whence was the standard to be derived? Liebig's polybasic 

 acids, and Dumas' substitution, had at length taught chemists 

 the difference between atom and equivalent, so that there 

 could no longer be any question with respect to the latter. 

 Recourse was again taken to Avogadro's hypothesis; but this 



