vi Preface 



meant to elucidate the text rather than to serve as 

 pictures. With the exception of those marked in the 

 list with an asterisk (*), which are adapted from other 

 sources, they were designed and drawn by the author 

 and Mrs. H. R. Mill for this book. The maps have 

 been specially compiled by Mr. J. G. Bartholomew, who 

 has spared no pains to make them accurate and complete. 



The book has been planned and written with the 

 constant advice and assistance of Professor Knight, 

 editor of the series, to whom the author desires to record 

 hearty thanks. Mr. Murray, the publisher of the series, 

 has also made valuable suggestions, and the title of the 

 book, The Realm of Nature, is due to him. 



Thanks are given to many of the author's teachers and 

 friends who have kindly revised the proofs of chapters 

 referring to the departments in which they are authorities, 

 especially to Professor P. G. Tait, Professor R. Cope- 

 land (the Astronomer-Royal for Scotland), Dr. A. Buchan, 

 Dr. John Murray of the Challenger, Professor James 

 Geikie, Mr. H. M. Cadell, Mr. J. Arthur Thomson, and 

 Mr. A. J. Ramsay. 



H. R. M. 



HERIOT-WATT COLLEGE, 



EDINBURGH, Atigust 1891. ' 



