of Valleys and Lakes. 297 



and opened a passage for the waters. It is only the philo- 

 sopher, who has deeply meditated on the effects which action 

 long continued is able to produce, and on the simplicity of the 

 means which nature employs in all her operations, who sees in 

 this nothing but the gradual working of a stream, that once 

 flowed over the top of the ridge which it now so deeply inter- 

 sects, and has cut its course through the rock, in the same way, 

 and almost with the same instrument, by which the lapidary 

 divides a block of marble or granite." And in the Alps (p. 122) 

 he shows that " the sharp peaks of the granite mountains .... 

 but mark so many epochs in the progress of decay," while the 

 loftiness of the harder peaks is due not to mere upheaval but to 

 the circumstance "that the waste and detritus to which all 

 things are subject will not allow soft and weak substances to 

 remain long in an exposed and elevated situation." "Thus, 

 with Dr. Hutton (p. 126), we shall be disposed to consider those 

 great chains of mountains, which traverse the surface of the 

 globe, as cut out of masses vastly greater, and more lofty than 

 anything that now remains." I could multiply sentences of 

 this kind from the writings of these great philosophers ; but 

 enough has been said to recall to memory the fact that before 

 the present race of " practical geologists " had written a line, 

 men of rare knowledge, keen sagacity, and the highest intel- 

 lectual powers, by appeals to nature already held those views 

 which some of their degenerate descendants have so readily repu- 

 diated, but to which a younger school show strong symptoms of 

 returning. I doubt also if some of the Swiss and Italian geolo- 

 gists will be quite content to stand godfathers to the opinion that 

 the Alpine valleys generally are apt to lie in lines of mere curva- 

 ture or fracture, whether close or gaping ; but without further 

 authority than that of personal conversation it would be impro- 

 per to quote their names. 



Unless I were to write a special elementary treatise on denu- 

 dation, enough has now been said to show that the theory of 

 formation of great systems of valleys by erosion in which water 

 and ice are main agents, is not a mere absurdity, and I do not 

 therefore care minutely to analyze the assertions that many of 

 the Alpine rivers " flow in fissures or deep chasms, . . . which 

 water alone never could have opened out;" or again, that the 

 Rhine and the Danube " never could have eroded those deep 

 abrupt gorges through which they here and there flow, and 

 which are manifestly due to original ruptures of the rocks." To 

 the neglected and even half-forgotten school of Hutton and 

 Playfair, and to many expert geologists of the present day whose 

 lives have been spent in practically analyzing the rocky struc- 

 tures of countries, the manifest nature of such " original rup- 



Phil. Mag. S. 4. Vol. 28. No. 189. Oct 1864. X 



