INTRODUCTION. 17 



greatest altitudes of Switzerland, points out to us the mode 

 in which nature is operating by decomposition, and the 

 attraction of gravitation. When standing on the borders 

 of the Mer de Glace, and while crossing its frozen bosom, 

 this operation was brought most forcibly to my mind. 

 Every moment my ears were saluted with the sound, more 

 or less distant, of rocks precipitated from some height into 

 the abysses below, and which reverberated over this frozen 

 sea. The time may come, when the pinnacles of Mont 

 Blanc and other mountains, which surround the beauti- 

 ful valley of Chaumonie, will have been precipitated to 

 their bases, and the debris be so completely carried off as 

 to leave, perhaps, that beautiful and fertile spot itself, the 

 highest pinnacle of the country, a naked rock, to be 

 gazed at from a distance.* 



Perhaps the most difficult point to solve, is that which 

 presents itself in the fact, that deposits in high latitudes 

 contain animal and vegetable remains, presumed by ana- 

 logy to be unable to exist in their temperature at the 

 present period. A change in the earth's axis would, of 

 course, affect the temperature of its surface, but whether 

 that can take place under any known law, in a sufficient 

 degree to effect such a change, has certainly not been 

 established. Sir John Herschel has supposed that a 

 change of temperature might take place in the change 

 of the elliptical orbit of the earth, which becomes gradu- 

 ally more circular, f 



* Since writing the above, I have observed the following passage in 

 Lyell's Principles of Geology, vol. 3. " Those naturalists who have 

 seen the glaciers of Savoy, and who have beheld the prodigious magni- 

 tude of some fragments conveyed by them from the higher regions of 

 Mont Blanc, to the valleys below, to a distance of many leagues, will be 

 prepared to appreciate the effects which a series of earthquakes might 

 produce in this region, if the peaks or ' needles,' as they are called, of 

 Mont Blanc, were shaken as rudely as many parts of the Andes have 

 been in our times." 



t Geol. Manual, p. 6. 

 C 



