PRINCIPLES OF GEOLOGY. 



CHAPTER I. 



Connexion between the subjects treated of in the former parts of this work and 

 those to be discussed in the present volume Erroneous assumption of the 

 earlier geologists respecting the discordance of the former and actual causes 

 of change Opposite system of inquiry adopted in this work Illustrations 

 from the history of the progress of Geology of the respective merits of the 

 two systems Habit of indulging conjectures respecting irregular and extra- 

 ordinary agents not yet abandoned Necessity in the present state of science 

 of prefixing to a work on Geology treatises respecting the changes now in 

 progress in the animate and inanimate world. 



HAVING considered, in the preceding volumes, the actual opera- 

 tion of the causes of change which affect the earth's surface and 

 its inhabitants, we are now about to enter upon a new division 

 of our inquiry, and shall therefore offer a few preliminary 

 observations, to fix in the reader's mind the connexion between 

 two distinct parts of our work, and to explain in what manner 

 the plan pursued by us differs from that more usually followed 

 by preceding writers on Geology. 



All naturalists, who have carefully examined the arrange- 

 ment of the mineral masses composing the earth's crust, and 

 who have studied their internal structure and fossil contents, 

 have recognized therein the signs of a great succession of former 

 changes ; and the causes of these changes have been the object 

 of anxious inquiry. As the first theorists possessed but a scanty 

 acquaintance with the present economy of the animate and 

 inanimate world, and the vicissitudes to which these are sub- 

 ject, we find them in the situation of novices, who attempt 

 to read a history written in a foreign language, doubting about 

 the meaning of the most ordinary terms; disputing, for 

 VOL. in. B 



