n6 From Matter to Man. 



crystals may here be summarised and their action 

 beautifully illustrated by evaporating solutions of 

 sugar, salt, or alum. If these substances be allowed 

 to cool slowly, the crystals are large and transparent ; 

 if suddenly, they are minute and opaque. Again, if 

 powdered alum and sulphate of copper be mixed and 

 then dissolved in hot water, the solution, on cooling, 

 shows the colourless crystals of alum and the blue 

 crystals of copper sulphate neatly separated from one 

 another. 



(a) All laws in their effects are swayed by control- 

 ling conditions. Like laws operating in like materials 

 produce different results at different times — small or 

 large crystals for instance — solely because environing 

 conditions differ. Slow motion involves slow selec- 

 tion, rapid motion rapid selection, with the consequent 

 corresponding productions, perfect and imperfect. In 

 crystallisation, as in other effects of the primary laws, 

 a law of selection obtains. Thus alum and copper 

 combine into distinct crystals by the simplest and 

 most fundamental law in nature — like-material-attrac- 

 tion or selection. This law also undoubtedly accounts 

 for the occurrence of separate beds of calc-spar, fluor- 

 spar, heavy-spar, fel-spar, quartz, etc. ; for in all prob- 

 ability the earth during the formation of those con- 

 stituents of its crust was a slowly cooling body, thus 

 allowing like-material-selection ample time to assert 

 itself. 



(/;) The fact that alum and copper sulphate are 

 compound substances evinces the influence of another 



