168 CORRELATION OF PHYSICAL FORCES. 



Undoubtedly, by approximating in theory the reactions of 

 inorganic and of organic chemistry, by keeping the mind 

 within the limits of a beaten path, instead of allowing it to 

 wander through a maze of isolated facts, the doctrine of com- 

 pound radicals has been of service ; but, on the other hand, 

 the indefinite variety of changes which may be rung upon the 

 composition of an organic substance, by different associations 

 of its primary elements, makes the binary constituents vary 

 as the minds of the authors who treat of them, and makes 

 their grouping depend entirely upon the strength of the anal- 

 ogies presented to each individual mind. From this cause, 

 and from the extreme license which has been taken in theo- 

 retic groupings deduced from this doctrine, a serious question 

 arises whether it may not ultimately, unless carefully re- 

 stricted, produce confusion rather than simplicity, and be to 

 the student an embarrassment rather than an assistance. 



