PKEFACE TO THE SECOND EDITION. 



Since, as stated in the Introduction (page 1), the 

 plan of this volume permitted only " a concise presenta- 

 tion of the facts," it was impossible to introduce either 

 full references to the illimitable literature of the subject 

 or detailed discussion of all disputed points. The facts 

 selected, therefore, were for the most part those upon 

 which it was supposed there would be pretty general 

 agreement. 



The discussion upon the subject of the continuity of 

 the Glacial period was, however, somewhat elaborate (see 

 pages 106-121, 311, 324, 332), and was presented with 

 excessive respect for the authority of those who maintain 

 the opposite view ; all that was claimed (page 110) being 

 that one might maintain the unity or continuity of the 

 Glacial period " without forfeiting his right to the respect 

 of his fellow-geologists." But it already appears that 

 there was no need of this extreme modesty of statement. 

 On the contrary, the vigorous discussion of the subject 

 which has characterized the last two years reveals a de- 

 cided reaction against the theory that there has been more 

 than one Glacial epoch in Quaternary times ; while there 

 have been brought to light many most important if not 

 conclusive facts in favour of the theory supported in the 

 volume. 



In America the continuity of the Glacial period has 

 been maintained during the past two years with impor- 



