PREFACE TO THE SECOND 

 EDITION 



In the present issue of this work Httle change has been 

 made except to correct a few errors which, in spite of care- 

 ful revision, had crept into the previous one. I hope that 

 now with the aid of my critics, whose services are gratefully 

 acknowledged, the book has been rendered free from any 

 serious mistakes. 



viU 



