iv The Hut Ionian Explanation of Valleys 1 8 1 



wards, ignored or explicitly rejected, even by those who 

 accepted the rest of their teaching. Hall, their friend and 

 associate, could not share their opinions on this subject. 

 Lyell too, who adopted so much of the Huttonian theory 

 and became the great prophet of the Uniformitarian 

 school, never would admit the truth of Button's doctrine 

 concerning the origin of valleys. Nor even now is that 

 doctrine universally accepted. It was Jukes who in 1862 

 revived an interest in the subject, by showing how com- 

 pletely the valley system in the south of Ireland was due 

 to the action of the rivers. 1 Eamsay soon after followed 

 with further illustrations of the principle. 2 But un- 

 questionably the most effective support to Hutton's teach- 

 ing has been given by the geologists of the United States, 

 who, among the comparatively undisturbed strata of the 

 Western Territories, have demonstrated, by proofs which 

 the most sceptical must receive, the potency of denudation 

 in the production of the topography of the land. 



To the Huttonian school belongs also the conspicuous 

 merit of having been the first to recognize the potency of 

 glaciers in the transport of detritus from the mountains. 

 Playfair, in his characteristically brief and luminous way, 

 proclaimed at the beginning of this century that " for the 

 removing of large masses of rock the most powerful 

 engines without doubt which nature employs are the 

 glaciers, those lakes or rivers of ice which are formed in 

 the highest valleys of the Alps, and other mountains of 

 the first order. . . . Before the valleys were cut out in 

 the form they now are, and when the mountains were 



1 Quart. Journ. Geol. Soc. xviii. (1862). 

 2 The Physical Geology and Geography of Great Britain, 1863. 



