PREFACE TO THE FIFTH EDITION. 



It is now more than three years since the appearance of the 

 last Edition of the Manual (published January, 1851). In that 

 interval the science of Geology has been advancing as usual 

 at a rapid pace, making it desirable to notice many new facts 

 and opinions, and to consider their bearing on the previously 

 acquired stock of knowledge. In my attempt to bring up the 

 information contained in this Treatise to the present state of 

 the science, I have added no less than 200 new Illustrations 

 and 140 new pages of Text, which, if printed separately and in 

 a less condensed form, might have constituted alone' a volume 

 of respectable size. To give in detail a list of all the minor 

 corrections and changes would be tedious ; but I have thought 

 it useful, in order to enable the reader of former editions to 

 direct his attention at once to what is new, to offer the follow- 

 ing summary of the more important additions and alterations. 



Principal Additions and Alterations in the present Edition. 



Chap. IX. — "The general Table of Fossiliferous strata," formerly 

 placed at the end of Chapter XXVII., is now given at p. 104, that the 

 beginner may accustom himself from the first to refer to it from time to 

 time when studying the numerous subdivisions into which it is now 

 necessary to separate the chronological series of rocks. The Table has 

 been enlarged by a column of Foreign Equivalents, comprising the names 

 and localities of some of the best known strata in other countries of con- 

 temporaneous date with British Formations. 



Chap. XIY. — XVI. — The classification of the Tertiary formations has 

 . been adapted to the information gained by me during a tour made in the 

 summer of 1851 in France and Belgium. The results of my survey were 

 printed in the Quarterly Journal of the Geological Society of London for 



