xii PREFACE. 



Science, South Kensington, tor invaluable services rendered, in posting the author in the latest 

 literature bearing upon many subjects dealt with in this volume, for placing him in com- 

 munication with specialists working at certain of the more obscure groups, and for substantial 

 assistance in the revision of the proof-sheets. 



The manner in which the author's photographs have been reproduced by the London 

 Stereoscopic Company and Messrs. Waterlow & Sons, is excellent beyond comment, and 

 Messrs. Riddle & Couchman have produced painstaking and faithful representations of the 

 author's original water-colour sketches. 



The thanks of the author are also due to the publishers, Messrs. W. H. Allen & Co., Limited, 

 who have throughout seconded his efforts to place the illustrations before the reader in the 

 most perfect manner possible, and who have spared neither trouble nor expense in everj' detail 

 of the production. 



London, February 24, 1893. 



