iii 



gratuitous and unexampled hypothesis for the solution o£ these analogous 

 facts." 



It is interesting to notice, too, in this work, published now more than 

 half a century ago, many striking anticipations of later geological disco- 

 veries — such as the action of water in producing volcanic eruptions, and 

 in causing the liquidity of lavas ; the presence of the same agent in 

 deep-seated rocks, and its iuflaence in the formation of those of granitic 

 character ; the effects of pressure in producing cleavage and foliation ; 

 and the necessarily more or less local character of all geological " forma- 

 tions." 



It must be confessed, howoA^er, that the ' Considerations on Yolcanos 

 was a work little calculated to promote the cause which the author and 

 his friend had so much at heart, namely, the removal of the prejudices 

 which hindered the progress of geological inquiry. Its bold and vigorous 

 attacks on the positions of the " Cataclysmists " roused their most deter- 

 mined opposition, while the numerous and sometimes rather crude specu- 

 lations into which the author allowed himself to be drawn, m. his attempt 

 at " the establishment of a new theory of the earth," afforded only too 

 many opportunities for telling retorts, which were eagerly taken advan- 

 tage of. 



In December 1826 Scrope was elected a Fellow of the Eoyal Society. 

 That he knew how to profit alike from the judicious criticism of 

 friends and the unsparing ridicule of opponents, was clearly enough shown 

 when in 1827 his second work, ' On the Geology and Extinct Yolcanos of 

 Central Erance,' made its appearance. In this essay, which is stiU 

 everywhere recognized as one of the classics of geological literature, the 

 author succeeded in demonstrating, even to the most incredulous, the 

 power of rivers to excavate the valleys in which they flow ; and his friend 

 Lyell pronounced a just eulogium on it when he said : — " We consider 

 Mr. Scrope's work the most able that has appeared since Playfair's 

 ' Illustrations of the Huttonian Theory,' in support of the doctrine that 

 ' valleys have been shaped out progressively by the action of rivers, or of 

 such floods as may occur in the ordinary course of nature.' " 



It was now the turn of LyeU to take the field in the controversy with. 

 the Catastrophists, and to bring to the support of the Huttonian doctrines 

 that vast mass of patiently collected facts, that moderation in statement 

 and candour in argument, and that calm, persuasive style — occasionally, 

 but involuntarily, flashing into eloquence — which gave such charm and 

 power to the ' Principles of Geology,' and which still recall so vividly to 

 all who knew him the deep enthusiasm, curbed by sound judgment, which 

 distinguished its author. 



During the composition of this great work the two friends were in 

 constant correspondence. Lyell had wisely determined to undermine the 

 positions of his adversaries, rather than to arouse their opposition by 



