IN" THE LAST HALF-CENTURY. 51 



period, enabled the composition of the so- 

 called 'organic' bodies to be determined 

 with rapidity and precision.* A large 

 proportion of these compounds contain 

 not more than three or fonr elements, of 

 which carbon is the chief ; but their num- 

 ber is very great, and the diversity of 

 their physical and chemical properties is 

 astonishing. The ascertainment of the 

 proportion of each element in these com- 

 pounds affords little or no help towards 

 accounting for their diversities ; widely 

 different bodies being often very similar, 

 or even identical, in that respect. And, 

 in the last case, that of isomeric com- 

 pounds, the appeal to diversity of ar- 

 rangement of the identical component 

 units was the only obvious way out of 

 the difficulty. Here, again, hypothesis 



* ' At present more organic analyses are made in a 

 single day than were accomplished before Liebig'a 

 time in a whole year. 1 — Ilofmann, Faraday Lecture, 

 p. 46. 



