EDITOR S PREFACE. vii 



I say that Dr. Burr's work will cause the deletion of 

 this senteuce if a new edition of Dr. Sharp's volume be 

 called for. 



I cannot let this volume appear without expressing mv 

 gratitude to Mr. G. A. K. Marshall for much time spent 

 in proof-reading, and for much help in other Editorial 

 tasks. 



A. E. SHIPLEY. 

 October 1909. 



