CREATION BY LAW. 261 



reference to Physical Causes, the other kind of 

 correlation has reference to those Mental Purposes 

 which Physical Causes are made to serve. These 

 two kinds of Correlation are perfectly distinct. 

 They are as distinct as the correlation of equal 

 pressures which a given volume of steam exerts 

 upon the opposite sides of a Boiler is distinct from 

 the correlation between that pressure and its con- 

 version into the driving force of cranks and wheels, 

 with all their adaptations for running on the rails, 

 or for paddling in the sea. They are as distinct as 

 the correlations of force developed in a Voltaic 

 Battery are distinct from the adjustments which 

 convert those forces into the means of communi- 

 cating Thought. 



Mr Darwin has not pointed out this distinction 

 • clearly. Indeed he does not seem to have had it 

 in his view. He groups under one name, the 

 Correlation of Growth, two classes of Pheno- 

 mena, which are indeed always combined in 

 fact, but which are entirely separate in idea. Cor- 

 relation of Growth in one sense is that law of 

 vital force which secures that any change in the 

 shape of one limb in an animal shall be accom- 



