cw 



PBEFACE. 



One object of the present volume — the appearance of 

 which has been long delayed by circumstances over 

 which I had no control — is to consider the objections 

 which have been urged from time to time against 

 the Physical Theory of Secular Changes of Climate 

 advanced in my work Climate and Time, and in 

 previous papers on the subject. Most probably I would 

 not have replied to my critics had it not been that the 

 examination of their objections afforded an excellent 

 opportunity for discussing more fully some compara- 

 tively obscure and difficult points in Geological 

 Climatology. Such discussion is the main and primary 

 object I have in view in the present volume. 



A chapter or two have been devoted to a fuller con- 

 sideration of the physical conditions of Continental 

 Ice than is to be found in Climate and Time. I have 

 also treated at greater length the question of the cause 

 of Mild Polar Climates, and likewise the growing 

 mass of evidence which we have in support of Arctic 

 Interglacial Periods. 



