PltKIACE. ^r- 



me n may perhaps be M'ell to mention here that, owincr 

 to the complete severance of communication between Greal 

 Britain and tlie enemy countries since the beginnino- of 

 hostilities, I have no knowledoe of any literature which may 

 I'ave appeared in the latter countries during the past two 

 years and a half. 



In conclusion, I must acknowledge my obligation to 

 l->r. Gr. A. K. Marshall for the punctilious care which he 

 has devoted to the preparation of my manuscript for the 

 press and the detection of errors and discrepancies, to 

 Mr. Horace Knight for the great pains he has bestowed 

 upon securmg the accuracy, as well as the artistic finish 

 of the Illustrations, and, lastly, to my wife for relieving me' 

 ot much of the more mechanical part of my work. 



G. J. ARROW. 



March, 1917. 



