30 LOUIS PASTEUE. 



at rest, the leaf wherein organic matter is created 

 by vegetable life. Terrestrial magnetism, the oppo- 

 sition which exists between the north and south 

 poles of a magnet, the opposition presented to us by 

 positive and negative electricity, are all the resultants 

 of dissymmetric actions and motions.' 



At the moment when Pasteur, entering upon the 

 labours which form the principal subject of this book, 

 abandoned the study of molecular physics and 

 chemistry which had previously occupied him, all 

 his thoughts were directed to the search of means 

 suited to render evident the influence of these causes 

 and these phenomena. At Strasburg he had procured 

 powerful magnets with the view of comparing the 

 actions of their poles, and, if possible, of introducing 

 by their aid, among the forms of crystals, a mani- 

 festation of dissymmetry. At Lille, where he was 

 nominated Dean of the Faculty of Sciences in 1854, 

 he had contrived a piece of clockwork intended to 

 keep a plant in continual rotary motion, first in one 

 direction and then in the other. ' All this was gross,' 

 he said to me one day ; ' but, further than this, I had 

 proposed, with the view of influencing the vegetation 

 of certain plants, to invert, by means of a hcliostat 

 and a reflecting mirror, the motion of the solar rays 

 which should strike them from the birth of their 

 earliest shoots, and in this direction there was more 



