Ch. I.] METHODS OF THEORIZING IN GEOLOGY. 7 



overthrown one after the other, which have been found quite 

 incapable of modification, and which are often required to be 

 precisely reversed. 



In regard to the subjects treated of in our first two volumes, 

 if systematic treatises had been written on these topics, we 

 should willingly have entered at once upon the description of 

 geological monuments properly so called, referring to other 

 authors for the elucidation of elementary and collateral ques- 

 tions, just as we shall appeal to the best authorities in 

 conchology and comparative anatomy, in proof of many posi- 

 tions which, but for the labours of naturalists devoted to 

 these departments, would have demanded long digressions. 

 When we find it asserted; for example, that the bones of a 

 fossil animal at QEningen were those of man, and the fact 

 adduced as a proof of the deluge, we are now able at once to 

 dismiss the argument as nugatory, and to affirm the skeleton 

 to be that of a reptile, on the authority of an able anatomist ; 

 and when we find among ancient writers the opinion of the gigan- 

 tic stature of the human race in times of old, grounded on the 

 magnitude of certain fossil teeth and bones, we are able to affirm 

 these remains to belong to the elephant and rhinoceros, on the 

 same authority. 



But since in our attempt to solve geological problems, we 

 shall be called upon to refer to the operation of aqueous and 

 igneous causes, the geographical distribution of animals and 

 plants, the real existence of species, their successive extinction, 

 and so forth, we were under the necessity of collecting together 

 a variety of facts, and of entering into long trains of reasoning, 

 which could only be accomplished in preliminary treatises. 



These topics we regard as constituting the alphabet and 

 grammar of geology ; not that we expect from such studies to 

 obtain a key to the interpretation of all geological phenomena, 

 but because they form the groundwork from which we must 

 rise to the contemplation of more general questions relating to 

 the complicated results to which, in an indefinite lapse of ages, 

 the existing causes of change may give rise. 



