HILL: GEOLOGY OF THE ISTHMUS OF PANAMA. 157 



to Mr. Josiah Pearcey, U. S. Consul, and Colonel Richard Wintersmith, 

 for their repeated favors and hospitality. I am also indebted to Mr. 

 Shaffer, of the Railway Company, who secured for me transportation and 

 boatmen for paddling down the Chagres and the completed portion of 

 the caual. 



After completing the section across the Isthmus T took the steamer 

 from Panama for Punta Arenas, Costa Rica. From the latter point I 

 made a section due east across that country to the Atlantic seaboard at 

 Limon. On this trip I was accompanied from San Jose to Port Limon 

 by Mr. Ahe Sjogren, whose valuable service is repeatedly mentioned in 

 the following pages. 



The large collections made by me upon the trip were kindly shipped 

 free of charge to Xew York upon the Colombian line of steamers by Colo- 

 nel Rives. In order to secure every possible light upon the collections, 

 I have received the aid of the following specialists, who have kindly 

 assisted me in making determinations. 



To Professor G. Brown Goode and Mr. W. J. McGee of the Smith- 

 sonian I am specially indebted for the use of the photographs in the 

 illustration of this report. Through their courtesy I was intrusted with a 

 fund for the purchase of objects of interest, and among those secured was 

 a superb collection of photographs of Isthmian and Costa Rican scenery. 



Thanks are also due to the Director of the U. S. Geological Survey for 

 the facilities placed at my disposal in preparing this report. 



The age of the fossiliferous beds and the determinations of the igneous 

 rocks are those of Dr. Wm. H. Dall of the U. S. Geological Survey, and 

 Professor J. E. Wolff of Harvard College, respectively. Their reports 

 upon the collections are printed as Appendices. 



Thanks are also due to Mr. R. M. Bagg, of Johns Hopkins University, 

 to whom were sent the Foraminifera ; to Professor F. H. Knowlton, for 

 his determination of fossil plants ; to Mr. T. TV. Stanton, who has assisted 

 me in the study of the Cretaceous rocks from Costa Rica and in the com- 

 parative studies of the Cretaceous faunas relative to the Isthmian prob- 

 lem ; to Mr. H. W. Turner, for microscopic studies of the fine earths ; 

 to Messrs. Paul and Ohm, of the Petrographic Laboratory of the U. S. 

 Geological Survey, for making sections of all the rocks ; and to Master 

 John R. Hudson, of the U. S. Geological Survey, for his assistance in 

 preparing maps and diagrams, as well as to Mr. Frank Burns, for cata- 

 loguing and numbering the collections. 



The reader should distinctly understand that this report should be 

 considered only in the light of a reconnoissance. An exhaustive study 



