X PEEFACE TO- THE FIFTH EDITION. 



geology, and in whicli the principal rocks composing the 

 earth's crust and their organic remains were described. In 

 subsequent editions this 4:th book was omitted, it having been 

 expanded, 1838, into a separate treatise called the "Elements 

 of Geology," first re-edited in 1842, and again recast and en- 

 larged in 1851, and entitled " A Manual of Elementary Geol- 

 ogy." Of this enlarged work another edition, called the 

 Fourth, w^as published in 1852. 



Although the subjects of both treatises relate to Geology, as 

 their titles imply, their scope is very different ; the "Princi- 

 ples" containing a view of the modern changes of the earth and 

 its inhabitants, while the " Manual" relates to the monuments 

 of ancient changes. In separating the one from the other, I 

 have endeavored to render each complete in itself, and inde- 

 pendent ; but if asked by a student which he should read first, 

 I would recommend him to begin with the " Principles," as 

 he may then proceed from the known to the unknown, and be 

 provided beforehand with a key for interpreting the ancient 

 phenomena, whether of the organic or inorganic world, by 

 reference to changes now in progress. 



It will be seen on comparing " The Contents" of the " Prin- 

 ciples" with the abridged headings of the chapters of the 

 present work (see the following pages), that the two treatises 

 have but little in common ; or, to repeat what I have said in 

 the Preface to the " Principles," they have the same kind of 

 connection which Chemistry bears to J^atural Philosophy, each 

 being subsidiary to the other, and yet admitting of being con- 

 sidered as difierent departments of science.'^ 



CHARLES LYELL. 



53 Harley-street, London, February 22, 1855. 



* As it is impossible to enable tbe reader to recognize rocks and minerals at 

 sight by aid of verbal descriptions or figures, he will do well to obtain a well- 

 arranged collection of specimens, such as maybe procured from Mr. Tennant (149 

 Strand), teacher of Mineralogy at King's College, London. 



