

PREFACE. 



'TPHE present work contains much that is new, and 

 much in correction and amplification of that 

 which is old ; and is intended as a closing deliverance 

 on some of the more important questions of geology, 

 on the part of a veteran worker, conversant in his 

 younger days with those giants of the last generation, 

 who, in the heroic age of geological science, piled up 

 the mountains on which it is now the privilege of their 

 successors to stand. 



J. W. D. 



Montreal 1893. 



