Ch. I.] METHODS OF THEORIZING IN GEOLOGY. 5 



relative level of sea and land, and doubts were then entertained 

 whether this change might be accounted for by the partial 

 drying up of the ocean, or by the elevation of the solid land. 

 The former hypothesis, although afterwards abandoned by 

 general consent, was at first embraced by a vast majority. A 

 multitude of ingenious speculations were hazarded to show 

 how the level of the ocean might have been depressed, and 

 when these theories had all failed., the inquiry, as to what 

 vicissitudes of this nature might now be taking place, was, as 

 usual, resorted to in the last instance. The question was agi- 

 tated, whether any changes in the level of sea and land had 

 occurred during the historical period, and, by patient research, 

 it was soon discovered that considerable tracts of land had 

 been permanently elevated and depressed, while the level of 

 the ocean remained unaltered. It was therefore necessary to 

 reverse the doctrine which had acquired so much popularity, 

 and the unexpected solution of a problem at first regarded as 

 so enigmatical, gave perhaps the strongest stimulus ever yet 

 afforded to investigate the ordinary operations of nature. For 

 it must have appeared almost as improbable to the earlier geolo- 

 gists, that the laws of earthquakes should one day throw light 

 on the origin of mountains, as it must to the first astronomers, 

 that the fall of an apple should assist in explaining the motions 

 of the moon. 



Of late years the points of discussion in geology have been 

 transferred to new questions, and those, for the most part, of 

 a higher and more general nature ; but, notwithstanding the 

 repeated warnings of experience, the ancient method of philo- 

 sophising has not been materially modified. 



We are now, for the most part, agreed as to what rocks are 

 of igneous, and what of aqueous origin, in what manner fossil 

 shells, whether of the sea or of lakes, have been imbedded in 

 strata, how sand may have been converted into sandstone, 

 and are unanimous as to other propositions which are not of a 

 complicated nature; but when we ascend to those of a higher 

 order, we find as little disposition, as formerly, to make a strenu- 

 ous effort, in the first instance, to search out an explanation in 



