28 LOUIS PASTEUR 



ones rotated it to the left. The paratartrate was 

 therefore a mixture of two substances, the right- 

 handed one proving to be in no way different from 

 ordinary tartrate. The paratartrates had no action 

 on the polarized ray because the rotary power of 

 one of the two ingredients neutralized that of the 

 other. 



This neat discovery aroused the enthusiasm of 

 the chemists of the Ecole Normale. Balard told 

 of it at the Institute de France where it awakened 

 the interest of Dumas and Biot. The latter, then 

 a man of seventy-four, was among the most promi- 

 nent of French scientists. Distinguished both in 

 astronomy and physics, and especially for his in- 

 vestigations on crystallography and the polarization 

 of light, he was naturally impressed with Pasteur's 

 observations. He had previously discovered the 

 different rotary effect of different crystals of 

 quartz, and when Balard told him of Pasteur's 

 experiments, he remarked, "It would be desirable 

 to examine closely this young man's results." 



Pasteur wrote to Biot whom he did not know 

 personally, but for whom he felt the admiration 

 which he was accustomed to cherish toward distin- 

 guished investigators in science, requesting the 

 pleasure of a visit in which he might exhibit his 



