xliv 



As a student at the Ecole JSTormale, Pasteur enjoyed the privilege 

 of attending the lectures both of Balard, at the Ecole Normale, and 

 of Dumas, at the Sorbonne. His energy was boundless, not even on 

 Sundays did he rest from his chemical studies, and on one of these 

 days of rest he actually succeeded in accomplishing the remarkable 

 feat of preparing no less than 60 grams of phosphorus from bones, 

 the operation lasting from four in the morning to nine o'clock at 

 night. 



But although Pasteur owed so much to each of those great masters 

 of chemical science, Balard and Dumas, it was a junior man, M. Dela- 

 fosse, who really directed the course which his researches should 

 take. A former pupil and assistant of the renowned Hauy, M. 

 Delafosse turned his pupil's attention to the study of crystals and to 

 problems of molecular physics, in which domain Pasteur's first laurels 

 were subsequently won. 



On completing his curriculum at the Ecole Normal e, Pasteur was 

 retained as assistant by Balard, and having now the opportunity of 

 carrying on research he determined to perfect himself in crystal- 

 lography, and set to work to repeat a very complete investigation 

 made by M. de la Provostaye, on the crystalline form of the tartrates. 

 It was soon evident, however, that mere repetition and confirmation 

 were not Pasteur's strong points, for although a comparative novice 

 at the kind of work in question, he was able to see what had escaped 

 the observation of his skilled predecessor in this field. Thus, both 

 on the crystals of tartaric acid itself, as well as on those of its salts, 

 he at once found small facets which had not hitherto been described. 



The presence of such facets on quartz crystals had not escaped the 

 attention of Haiiy, who indeed had further divided such quartz 

 crystals into left and right-handed quartz, according to the side on 

 which these facets were developed. Biot, again, in his extended in- 

 vestigations on polarisation, had found that some specimens of 

 quartz turn the plane of polarisation to the right and some to the 

 left, whilst Sir John Herschel, in 1820, suggested that the two 

 phenomena were connected, and that the left-handed quartz crystal 

 rotated the plane of polarisation in one direction, the right-handed 

 in the other. Experiments showed that this was actually the case. 

 These remarkable relations appear to have made a profound impres- 

 sion on young Pasteur, and so deeply imbued was he with the idea 

 that polarimetric effect must be associated with crystalline form, 

 that the appearance of these hemihedral faces (as these facets are 

 technically called) seemed to him of the very highest importance, 

 and to deserve the most careful study. To this end he prepared no 

 less than nineteen different 'tartrates, and found that all exhibited 

 hemihedral faces. Pursuing his minute examinations of these 

 crystals, he found that whilst the crystals of the inactive tartaric 



