10 PASTEUR AND AFTER PASTEUR 



chemistry ; nothing more than the offer of a small 

 appointment, and the business of submitting theses 

 for a degree. The revolution of 1848 stirred him 

 to enrol himself in the Garde Nationale, and to 

 give his small savings to the cause of the Republic. 

 " I am writing to you," he says in one of his 

 letters home, " from the Orleans Railway, where I 

 am on duty with the Garde Nationale. I am 

 thankful that I was in Paris through these February 

 days, and that I am still here. I should be sorry 

 to leave Paris just now, with all these beautiful 

 grand ideas unfolding themselves before my eyes. I 

 would fight heart and soul, if need be, in the sacred 

 cause of the Republic." A few months later, came 

 the greatest sorrow and the greatest happiness 

 which had yet come to him his mother's death, 

 and his first discovery in science : he discovered 

 the molecular disymmetry of tartaric acid. 



His study of tartaric acid and the tartrates was 

 founded on the fact that certain crystalline sub- 

 stances quartz, crystallising sugar, quinine rotate 

 the plane of a ray of polarised light. They retain 

 this power, even if they be dissolved : thus, a 

 solution of the crystals of sugar has the same action 

 as the crystals themselves. But there are two 

 forms of quartz : each of them belongs to the same 

 order of crystals, each of them is quartz : for prac- 

 tical purposes, there is no difference between them : 



