a 



OP 



llj^^^ 



"^^unt of 



THE BEGINNINGS OF LIFE. 



61 



•ic chl 



as 



oride 



t 



^Jually b 



s 



ulphate 



)\ 



y Diet 

 are 



consideration of the circumstances under which such 

 substances are found naturally, as crystalline minerals, 

 makes it probable that they have also resulted from 



-^Pitate. It 



^nsolubl 



e 



l^^borat 



COH| 



double decompositions 

 slowness. 



brought 



about with great 



07 as 



amo: 



react 



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- 



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



mes, wooden I; curing a long list of crystallized minerals similar to 

 or other of those which had hitherto been known to exist only in 



insoluble salts i mineral veins and other situations^. 



* sulphates ofk Variation in the ^conditions' under which the crystal- 



form of 



^^y be obtains 

 chemical 



owly. This 



/ 



1 



1 



5 of baryta 



lization of any particular substance occurs, often gives 



- -t and seven ^^^^ ^^ ^^^^ most marked variation in its crystalline 



interesting bec 



form 



Thus, referring to the article ^Dimorphism' in 



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



statements : — ^ Many substances, both simple and com- 



ment,^''* pound, crystallize in forms which belong to two or three 



- stated:— 'Th^^^^ different systems of crystallization, or which, even if 



lid state, and *^ 



A the ff^^^^^' ^^^ ^^ obtain a number of crystals irregularly formed and interlacing 

 ^^^ Alpdor=? each other in all directions.' The transition between small, ill-formed 



I vent be cooler 

 all andiU^ .^^^ 

 ^ body ^^'' a 



/, 



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

 still greater rapidity of separation. 



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

 Association' for 1836. 

 ^ See Fig. 44. 



:les solidify' J^ 



ions attach tb 



