PREFACE. Vii 



An attempt has been made to give some historical value 

 to the work by indicating the labours of the many geologists 

 to whose observations our present knowledge is due. Thus 

 the foot-notes are confined almost entirely to original 

 memoirs, and they are with few exceptions the result of 

 personal research. 



Without the friendly co-operation and the sympathy of 

 many geologists the work, however, could never have been 

 accomplished, and the writer is under great obligations to 

 some of them for pointing out mistakes and omissions in 

 the former edition, and to others for revising proofs of 

 the present one. He is more especially indebted to Prof. 

 Bonney, Mr. Horace T. Brown, Mr. Champernowne, Mr. 

 Goodchild, Mr. W. Gunn, Mr. P. F. Kendall, Mr. T. M. 

 Hall, Dr. Hicks, Prof. Hughes, Prof. Hull, Mr. Jukes-Browne, 

 Prof Lebour, Mr. Mellard Reade, Mr. Clement Reid, Mr. 

 Rudler, Mr. Rutley, Mr. Topley, Mr. Ussher, Mr. Whitaker, 

 Mr. Edward Wilson, and Mr. B. B. Woodward. Many 

 serious errors have thus been avoided ; but it must be 

 understood, at the same time, that the friends above 

 mentioned are not responsible for any facts or opinions, 

 unless where expressly stated, for their suggestions have 

 not in all cases been adopted. 



To the Councils of the Geological Society and of the 

 Geologists' Association, as well as to the respective authors, 

 the writer is indebted for permission to reproduce many 

 illustrations published by those Societies. Dr. Henry 

 Woodward has also kindly lent a number of blocks that 

 have illustrated the pages of the " Geological Magazine." 

 Several views of the Isle of Purbeck have been reproduced 

 from etchings by Mr. Alfred Dawson. Other illustrations 

 have been specially prepared for this new edition, including 



