there is disymmetry in bulk, and there is molecular 

 disymmetry. 



In October, 1844, Biot had communicated to the 

 Academic des Sciences a note, by Mitscherlich, on 

 the action of tartaric acid and the tartrates on 

 polarised light. Pasteur had studied this note : 

 and he had been shown, by Auguste Laurent, the 

 different forms of sodium tungstate : 



" One day, M. Laurent happened to be working, 

 if I remember rightly, at sodium tungstate the 

 crystals were perfect, they had been made according 

 to the directions of another chemist, whose results 

 he was verifying and he showed me, under the 

 microscope, that this salt, which looked so homo- 

 geneous, was plainly a mixture of three kinds of 

 different crystals, which anybody fairly accustomed 

 to crystalline forms w T ould easily recognise. This 

 fact, and many others of a like nature, made me 

 understand how much might be gained, in chemistry, 

 from a knowledge of crystalline forms. M. Delafosse, 

 our professor of mineralogy, a man of great modesty 

 and great distinction, had long ago taught me to 

 love crystallography. So, to get into the way of 

 measuring the angles of crystals, I set myself to 

 work hard at the forms of a very fine series of 

 compounds, which all crystallise very easily- 

 tartaric acid and the tartrates. ... I had another 

 reason for making a special study of these forms. 

 M. de la Provostaye had just published his work on 

 them, which gave almost everything : so I could 

 always be comparing my observations with the 

 precise observations of an expert in physics." 



