PREFACE 



TO 



THE TENTH EDITION 



In the Preface to the First Volume I gave a list of the dates 

 of publication of the successive editions of this treatise^ as 

 well as of my ' Elements of Geology ' and my ' Antiquity of 

 Man/ and pointed out the relation of these two last works 

 to the ' Principles/ 



In the same Preface I 



made 



ofave a list of the chief additions 

 first time ; pointing out, so far as was 

 possible, the corresponding pages in tlie ninth edition; so 

 that readers ah-eady familiar with the earlier editions might 

 be able at once to refer to what was new. 



T -now snhioin a, similar list of the chief alterations and 



additions introduced for the first time into this tenth edition. 



>/ 



>/ tlie Tenth Edition of the ' Principles of 



Ninth 

 Edition. 



Page 



396 



to 



424 



Tenth 

 Edition. 

 Vol. 11. 



Page 

 1 



to 



47 



Additions and Corrections. 



Considerable additions have been made to this Twenty-sixth 

 Chapter, on the structure of Mount Etna, in consequence 

 of my re-examination in 1857 and 1858 of this yolcano, 

 which I had first visited thirty years before, in 1828. 

 The theory of a double axis of eruption is explained (p. 9), 

 and the changes in the scenery of the Val del Bove, caused 

 by the lavas of 1852, are described (p. 31). ^ The solid 

 texture and steep original inclination of certain lavas of 

 known date are pointed out (pp. 35 & 36). The relation 

 of some ancient valleys on Etna to the former structure 

 of the mountain is considered (p. 40). 



