HI LECTURES ON EVOLUTION 51 



and water. This view was held more or less 

 distinctly, sometimes combined with the notion of 

 recurrent cycles of change, in ancient times ; and 

 its influence has been felt down to the present day. 

 It is worthy of remark that it is a hypothesis 

 which is not inconsistent with the doctrine of 

 Uniform itarianism, with which geologists are 

 familiar. That doctrine was held by Hutton, and 

 in his earlier days by Lyell. Hutton was struck 

 by the demonstration of astronomers that the per- 

 turbations of the planetary bodies, however great 

 they may be, yet sooner or later right themselves; 

 and that the solar system possesses a self-adjusting 

 power by which these aberrations are all brought 

 back to a mean condition. Hutton imagined that 

 the like might be true of terrestrial changes ; 

 although no one recognised more clearly than he 

 the fact that the dry land is being constantly 

 washed down by rain and rivers and deposited in 

 the sea ; and that thus, in a longer or shorter time, 

 the inequalities of the earth's surface must be 

 levelled, and its high lands brought down to the 

 ocean. But, taking into account the internal 

 forces of the earth, which, upheaving the sea-bot- 

 tom give rise to new land, he thought that these 

 operations of degradation and elevation might com- 

 pensate each other ; and that thus, for any assign- 

 able time, the general features of our planet might 

 remain what they are. And inasmuch as, under 

 these circumstances, there need be no limit to the 



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