EDITORS PREFACE 



This Series is primarily designed to aid the University Extension 

 Movement throughout Great Britain, and to supply the need so 

 widely felt by students, of Text-books for s-tudy and reference, in 

 connection with the authorised Courses of Lectures. 



The Manuals differ from those already in existence in that they 

 are not intended for School use, or for Examination purposes ; and 

 that their aim is to educate, rather than to inform. The statement 

 of details is meant to illustrate the working of general laws, and the 

 development of principles ; while the historical evolution of the 

 subject dealt with is kept in view, along with its philosophical 

 significance. 



The remarkable success which has attended University Extension 

 in Britain has been partly due to the combination of scientific treat- 

 ment with popularity, and to the union of Duplicity with thorough- 

 ness. This movement, however, can only reach those resident in the 

 larger centres of population, while all over the country there are 

 thoughtful persons who desire the same kind of teaching. It is for 

 them also that this Series is designed. Its aim is to supply the 

 general reader with the same kind of teaching as is given in the 

 Lectures, and to reflect the spirit which has characterised the move- 

 ment, viz. the combination of principles with facts, and of methods 

 with results. 



The Manuals are also intended to be contributions to the Literature 

 of the Subjects with which they respectively deal, quite apart from 

 University Extension ; and some of them luill be found to meet a 

 general rather than a special want. 



They will be issued simultaneously in England and America. 

 Volumes dealing with separate sections of Literature, Science, 

 Philosophy, History, and Art have been assigned to representative 

 literary men, to University Professors, or to Extension Lecturers 

 connected with Oxford, Cambridge, London, and the Universities of 

 Scotland and Ireland. 



A list of the works in this Series will be found at the end of the 

 volume. 



