vi PREFACE. 



from my friends and pupils. Had it not been for their 

 co-operation a large number of the disputed points, which 

 I have been able to investigate during the preparation of 

 the work, must have been left untouched. 



My special thanks are due to Mr Sedgwick, who has 

 not only devoted a very large amount of time and labour 

 to correcting the proofs, but has made for me an index of 

 this volume, and has assisted me in many other ways. 



Dr Allen Thomson and Professor Kleinenberg of 

 Messina have undertaken the ungrateful task of looking 

 through my proof-sheets, and have made suggestions 

 which have proved most valuable. To Professors 

 Parker, Turner, and Bridge, I am also greatly indebted 

 for their suggestions with reference to special chapters of 

 the work. 



