5 04 SCIENCE PROGRESS. 



time, none can deny the services which theories based on 

 the property of valence have rendered to stereochemistry, 

 especially in the hands of van't Hoff, whose views we have 

 presently to consider. If we have thus far postponed an 

 account of the work of the investigator who first opened up 

 this branch of chemistry, it is because the theories involved 

 have proved so fascinating that they have caused the general 

 considerations underlying them, and more especially repre- 

 sented by Le Bel, to be very largely neglected ; and also 

 because a mind once occupied with a particular idea as to 

 the direction of the valences of any atom in a molecule, 

 finds it difficult to gain an unprejudiced view of the 

 structure of the molecule as a whole. 



Arnold Eiloart. 

 ( To be continued. ) 



