26 ON CHANGES IN THE DISPOSITION 



abouthypotheses resting on such knowledge and talents 

 as have been displayed by the Kirwans and the De 

 Lues. They are portions of dreams that will be suf- 

 ficiently examined hereafter: my present business is 

 with facts and evidence, not with anile conjectures. 

 When La Place shall tell me that such things have 

 been, it will then be time to enquire what they have 

 done. If other evidence of such currents has been 

 imagined, in the waste of sea shores, here also I see 

 nothing but the tedious eifects of daily actions ; as I 

 leave to another set of theorists to produce them by 

 " convulsions of nature." I know not why we must 

 believe that England was ever joined to France, at 

 Dover, because both shores possess chalk cliffs: if 

 these are to be our conclusions, whence are there any 

 islands in the world? If it be that Britain was peopled 

 with animals at an early period, why is New Holland 

 thus peopled, or how carne plants on St. Helena? This 

 is but another form of the theory which will not 

 permit even mountains and valleys to have been pro- 

 duced by the original elevation of the strata. 



I have not thought it necessary to bestow a separate 

 section on the destructive powers of the sea, and it is 

 perhaps best examined here; since it will at the same 

 time answer this speculation. The evidence is every 

 where ; but the causes are those already discussed ; and 

 a just examination of the facts will prove it to be so. 

 The cliffs of rocky shores fall, for the same reasons 

 that those of the interior mountains do ; the sea carries 

 the materials away, after it has pulverized them, just 

 as it removes the alluvia of rivers; and as far as itself 

 aids in this destruction, it is by the force with which 

 its waves, aided by these fragments, assail their bases. 

 There is no stream of the ocean which can, of itself, 

 wear away a rocky shore; and that which is now, is 



