Preface xv 



To Mrs R. B. Goodden I am indebted for several 

 valuable hints, and much suggestive criticism while the 

 writing of the book was in progress. 



To my wife, my thanks are, as always, due for assist- 

 ance of every kind, and for using curb and spur as need 

 was. Her power of critical judgment, her accuracy and 

 originality of thought, have been invaluable. Besides 

 this more general assistance she further undertook the 

 dull labour of compiling the synopsis and of revising 

 the book in proof. 



The blame of faults of all kinds must rest only on 

 myself, the credit of some thoughts that are of value 

 must be shared with these my friends. 



S. A. McD. 



WlNTON, 



January 1918. 



6.- 



