iv PREFACE. 



These studies make little claim to systematic unity. Unity 

 of a certain sort, indeed, they will be found to possess, namely, 

 unity of purpose and of point of view, but not that of the mono 

 graph or treatise. There is one omission, however, which we 

 especially regret. After considerable prominence is given to the 

 theory of relations in the first and second parts, the subject is 

 only incidentally treated in the third. But one of the writers 

 having been forced to withdraw from the w r ork, the attempt to 

 supply this omission would have meant the indefinite postpone 

 ment of publication. 



The book is the product of a genuine collaboration. Some 

 division of labor was necessary at the outset ; but almost endless 

 discussion, together with repeated revision by both writers, has 

 made the work in a peculiar sense our common property. 



BRYN MAWR COLLEGE, 

 September 12, 1910. 



