iv PREFACE. 



which an attempt is made to point out the bearing on geology 

 of the modern changes of the earth, and to which is prefixed 

 a history of the opinions which have been entertained in this 

 science, from the times of the earliest writers to the present 

 day. 



The volume, therefore, now offered to the public, is neither 

 an epitome of the Principles, nor an abridgement of any part 

 of that work. In some places, where I thought it desirable 

 to incorporate in the Elements certain passages of the former 

 work, I have not abridged what was previously written, but 

 have expanded it, giving fuller explanations, and additional 

 wood-cuts, in the hope of rendering it more intelligible to the 

 beginner. 



> Through the kindness of two of my friends I have been 

 enabled to refer frequently to two works, not yet before the 

 public, Mr. Darwin's Journal of Travels in South America, 

 1832 to 1836, &c., and Mr. Murchison's Silurian System ; 

 the last of which was presented to me complete, with thei ex- 

 ception of the maps and plates, and will shortly be published. 

 Mr. Darwin's Journal was finished, and ready for publica- 

 tion, some time before the printing of my MS. had begun, but 

 is still detained, to the great regret of the scientific world, 

 because it is to form part of a larger work, including an 

 account of the Surveys of Captains King and FitzRoy, in 

 South America. 



