collecting and summarizing this information for the layman I 

 have endeavored in every way to see that the original investi- 

 gators receive full credit for whatever of their results I may 

 have used. I regret the impossibility of naming the many 

 artists-, engravers, preparators, field assistants and others who 

 from the earliest days have conscientiously and in a painstaking 

 way contributed to the grand total of accomplishment. Their 

 work has been essential and in the original literature has in 

 general received full recognition. A reasonable regard has been 

 entertained for the relative importance of the varied kinds of in- 

 vestigation. Necessarily countless details of description have 

 been omitted, but care has been taken throughout to see that 

 brevity of description has not necessitated sacrifice of accuracy. 

 My gratitude extends in many directions for literature con- 

 sulted and for material used. I am indebted particularly to the 

 Koote Mineral Company of Philadelphia for permission to re- 

 produce from their Catalogue of Minerals Plate No. 15, and to 

 Mr. Henry R. Knipe of Tunbridge Wells for permission to 

 reproduce Plates Nos. 24, 30, 39, originally drawn by Mr. T. 

 vSmit for the volume "Nebula to Man" recently published by 

 Messrs. J. M. Dent & Company of London. In an especial way 

 I am indebted to Professor Henry F. Osborn and the American 

 Museum of Natural History of New York, through whose 

 generosity I have been permitted to use the copyrighted photo- 

 graphic prints reproduced in Plates Nos. 27, 29, 32, 40, 42, 47 

 and Figure 1 of No. 33, the originals of which, from drawings 

 and paintings made by Mr. Charles R. Knight under the direc- 

 tion of Professor Osborn, are in the American Museum of 

 Natural History. Lastly I wish to record my appreciation of 

 favors rendered by President Charles H. Fulton and the Regents 

 of Education. It is due them to state that their hearty coopera- 

 tion has greatly added to whatever value the paper may possess 

 and has augmented in no little degree my interest in its 

 preparation. 



