PREFACE. XXV 



was indispensible to say. It has been attempted 

 however to limit those remarks rigidly to that 

 which may be considered the natural history of 

 the different rocks ; or to mere details of matters 

 of fact respecting the general characters and re- 

 lations of the larger masses which constitute the 

 earth's surface. Thus far therefore the follow- 

 ing work comprises the elements of geological 

 science. But that science is not limited to a 

 mere history of rocks ; as, independently of the 

 highly important branch of organic mineralogy, 

 it involves the consideration of actions and events, 

 and an enquiry after causes, for which no room 

 could here have been found ^without adopting a 

 plan entirely different ; without combining, in 

 one word, a general treatise on geology with a 

 detailed catalogue of all the rocks in nature. It 

 seemed expedient to keep these two works sepa- 

 rate ; that the manual of the student might be 

 less encumbered with unnecessary matter; and 

 that more ample room might be reserved for dis- 

 cussions which could not have been crowded, 

 without great inconvenience, into a narrow space ; 

 that speculations and theories might, in short, be 



