THE BEGINNINGS OF II FE. 8l 



the injured form of a crystal is restored when it is 

 placed under suitable conditions, because such a crys- 

 talline form is to be regarded as the physical expression 

 of that mode of aggregation under which alone (within 

 certain narrrow limits) a polar equilibrium of its mole- 

 cules can exist ^. If there is not such a connection 

 between particular crystalline forms and certam kinds 

 of matter under the influence of given conditions, 

 then, what reason would there be for the uniform 

 similarity of result which is observable ? Why should 

 different substances have definite crystalHne forms? 

 Whilst, on the other hand, if a relationship of this 

 kind does exist, it is more easy for us to understand 

 that the repair of a broken crystal should be effected 

 with such undeviating regularity. The molecules of 

 any kind of matter, when under the simultaneous 

 influence of different forces, ultimately tend to lapse 

 into a state of more or less stable equilibrium 2. 

 If further proof were needed of the truth of this view, 



^ On this subject Mr. Lewes says (loc. cit. p. 623): — 'That it is the 

 polarity of the molecules which, at each moment, determines the group 

 those molecules will assume, is well seen in the experiments of Lavalle, 

 mentioned by Brown {Morpholog.Studien uher die Gestaltting-Gesetze, iSCfS). 

 He showed that, if when an octohedral crystal is forming, an angle be 

 cut away so as to produce an artificial surface, a similar surface is 

 produced spontaneously on the corresponding "angle, whereas all the 

 other angles are sharply defined.' This cutting away of the angle of 

 the crystal is a change which does not interfere with the essential nature 

 of the crystalline form, so that the polar balance may be perfectly 

 restored by the formation of another opposing flat surface. 



2 Spencer's ' First Principles,' 2nd ed. pp. 484, 495. 



VOL. II. G 



