4 Preface 



opinion as to the justice of such selection as I have 

 made and as to the omissions I have felt necessary. 

 On such points I shall welcome the criticism of my 

 readers with great cordiality, recognizing fully what 

 variety of opinion may exist on the details of every 

 subject. I claim, however, to have made a sincere 

 attempt to give credit where it is due and to judge 

 no one unfairly. 



In one respect I have departed from the plan of 

 Sachs' volume ; I have given a bibliography as full 

 and as complete as I have been able to compile of the 

 works to which I have found occasion to refer. 



I wish to express my acknowledgements of the kind 

 assistance of Dr. Francis Darwin, of Dr. D. H. Scott, and 

 of Dr. A. B. Rendle, who have read certain chapters of 

 the manuscript, and to thank Professor Harvey Gibson, 

 and especially Professor S. H. Vines, for much kindly 

 help and criticism as the work was passing through 

 the press. 



CAMBRIDGE, 

 1909. 



