PASTEUR: 

 THE HISTORY OF A MIND 



FIRST PART 



WORKS ON CRYSTALLOGRAPHY 

 I 



THE PREDECESSORS OF PASTEUR: HAUY, WEISS, 

 DELAFOSSE 



If we wish to take exact account of the progress 

 brought about in science by the different studies of Pas- 

 teur, the first thing to do is to become acquainted with 

 the state of our knowledge up to the time when each one 

 of these studies advanced it. In order to understand 

 clearly the progress they have made, we must know from 

 what they started. But that is not as easy as we might 

 think. To get an idea of the general intellectual status 

 of any period one must not content himself with reading 

 the classical books and manuals of the epoch: these 

 books are always behind the knowledge of the labora- 

 tories, that which is in the air, that which one breathes, 

 and which arouses investigators. We encounter another 

 danger in resorting to sources and original memoirs; 

 viz., the danger of taking the opinions and ideas of their 

 authors for current opinions and ideas. A scientific 

 man worthy of the name is always in advance of his con- 

 temporaries: between him and them is a middle zone in 

 which one must take his stand in order to judge the under- 

 takings and the progress of a period; but where is one to 

 find this middle ground, and how, when he has found it, 



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