Vlll PREFACE. 



dwelling of man. The deep interest taken in such 

 inquiries has created a great and general demand 

 for information on these subjects, especially with 

 persons who, — unable, from want of time or of the 

 necessary preparation, to enter into the study of 

 the actual phenomena, — must necessarily be satis- 

 fied with receiving the results obtained by others. 

 To the desire to supply this want, which is 

 strikingly illustrated by the almost simultaneous 

 publication of several Treatises on similar sub- 

 jects, these Letters on the Physics of the Earth 

 owe their origin. In their publication, it was 

 not so much the Author's object to offer new 

 facts to the man of science, as to render to a 

 large circle of readers some assistance towards 

 obtaining clearer views and more precise notions 

 of the processes which are at work, on the largest 

 scale, on this our Earth, of the causes by which 

 they are governed, and of their influences on the 

 condition and general features of the surface of 

 the Globe. His Letters are addressed to a person 

 not supposed to have any greater amount of scien- 



