SCIENCE AND WAR 315 



J. B. Biot bad entered (In- ranks <>f - 

 of the Eeole Polyteohniqne and tin- artillery s< ; 

 In 1819 he had announced that tin- plane of j 

 ized light for example, a ray passed through Ice- 

 land spar is deflected to right or left by v:r 

 chemical substances. Among these is common tartarie 

 acid the acid of grape-juice, obtained from wine 

 lees. Racemic acid, however, which is identical \\ith 

 tartaric acid in its chemical constituents, is optically 

 inactive, rotating the plane of polarized light neither 

 to the right nor the left. This substance Pasteur 

 subjected to special investigation. He scrutinized 

 the crystals of sodium ammonium racemate obtained 

 from aqueous solution. These he observed to be of 

 two kinds differing in form as a right glove from a 

 left, or as an object from its mirror-image. Separat- 

 ing the crystals according to the difference of form, 

 he made a solution from each group. One solution, 

 tested in the polarized-light apparatus, turned the 

 plane to the right ; the other solution turned it to the 

 left. He had made a capital discovery of far-reaching 

 importance, namely, that racemic acid is composite, 

 consisting of dextro-tartaric and laBVO-tartaric acids. 

 Biot hesitated to credit a mere tyro with such an 

 achievement. The experiment was repeated in his 

 presence. Convinced by ocular demonstration, he 

 was almost overcome with emotion. u My dear boy," 

 he exclaimed, "I have loved the sciences so much 

 my life through that that makes my heart jump." 



Pasteur began his regular professional experience 

 as a teacher of physics in the Dijon lycee, but he was 

 soon transferred to the University of Strasburi; 

 (1849). There he married the daughter of the 



