THE BEGINNINGS OF LIFE. 57 



consideration of the circumstances under which such 

 substances are found naturally, as crystalline minerals, 

 makes it probable that they have also resulted from 

 double decompositions brought about with great 

 slowness. 



It was, moreover, ascertained by M. Becquerel and 

 Mr. Robert Were Fox, that many crystalline minerals 

 which had not previously been procured artificially, 

 were to be obtained by the long-continued action of 

 weak galvanic currents upon solutions containing the 

 necessary ingredients. These investigations were after- 

 wards taken up by Mr. Crosse, who succeeded in pro- 

 curing a long list of crystallized minerals similar to 

 those which had hitherto been known to exist only in 

 mineral veins and other situations \ 



Variation in the Conditions' under which the crystal- 

 lization of any particular substance occurs, often gives 

 rise to the most marked variation in its crystalline 

 form 2 . Thus, referring to the article c Dimorphism' in 

 Watts's c Dictionary of Chemistry,' we find the following 

 statements : c Many substances, both simple and com- 

 pound, crystallize in forms which belong to two or three 

 different systems of crystallization, or which, even if 



thus we obtain a number of crystals irregularly formed and interlacing 

 each other in all directions.' The transition between small, ill-formed 

 crystals and mere amorphous granules, is easily to be accounted for by a 

 still greater rapidity of separation. 



1 For a brief account of these experiments, see ' Report of British 

 Association' for 1836. 



2 See Fig. 44. 



