PREFACE. 



'HP HE present work contains much that is new, and 



much in correction and ampHfication 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. 



