IN THE LAST HALF-CEXTUKY. 49 



was the creation of a system of symbolic 

 notation, which, not only made the nature 

 of chemical compounds and processes eas- 

 ily intelligible and easy of recollection, 

 but, by its very form, suggested new lines 

 of inquiry. The atomic notation was as / 

 serviceable to chemistry as the binomial 

 nomenclature and the classificatory sche- 

 matism of Linnaeus were to zoology and 

 botany. 



Side by side with these advances arose in biolo- 

 another, which also has a close parallel in fheoryof 

 the history of biological science. If the ™° s trac- 

 unit of a compound is made up by the ture * 

 aggregation of elementary units, the no- 

 tion that these must have some sort of 

 definite arrangement inevitably suggests 

 itself ; and such phenomena as double de- 

 composition pointed, not only to the ex- 

 istence of a molecular architecture, but to 

 the possibility of modifying a molecular 

 fabric without destroying it, by taking 



out some of the component units and 

 4 



