14 PASTEUR: THE HISTORY OF A MIND 



which have these facets, and of the paratartrates which 

 do not have them. He could not have much considera- 

 tion for these hemihedral facets which sometimes upset 

 a parallelism, otherwise so marked. With a slight 

 exaggeration we may say that Mitscherlich did not wish 

 to see them and did not see them, while Pasteur, who 

 wished to see them, saw them at once. 



It must be stated, however, that these facets are not 

 always very apparent in all the tartrates and in all the 

 crystals of the same tartrate, but we can ordinarily make 

 them more manifest by changing slightly the conditions 

 of crystallization. In short, as soon as attention is 

 called to them and we search for them, we find them in 

 all of the tartrates. 



This confirmed the idea of a correlation between hemi- 

 hedrism and the rotary power, but this correlation was 

 still remote. In appearance at least not even here 

 was there that correlation between the position of the 

 facet and the direction of rotation which made the right- 

 handed quartz the right-handed plagihedron, and the 

 left-handed quartz the left-handed plagihedron. The 

 crystals of the different tartrates belong to different 

 systems, and have therefore very different aspects, and 

 we do not find that beautiful harmony of forms which 

 makes almost twin brothers of the different prismatic 

 crystals of quartz. The confirmation which Pasteur 

 had just made would have remained fruitless without 

 another discovery to give it the life it still lacked, and 

 if the first discovery belonged to the man of reflection 

 and imagination the latter was due to the experimenter. 



I have just said that the crystals of the different 

 tartrates have the most varied aspects; there are needles, 

 tabular crystals, and prisms; they are more or less 

 covered with facets which cut off their angles or their 

 edges and mask their primitive form. But in spite 



