PREFACE. 



Geologists generally recognize that knowledge of the geology of 

 Central America is essential to solving the problems of the geologic 

 history of the Americas, and many of them have devoted as much 

 thought and study to the region as their rather occasional oppor- 

 tunities for investigation permitted. Among the previous investiga- 

 tors T. A. Conrad, W. M. Gabb, J. W. Gregory, W. H. Dall, H. Dou- 

 ville, P. Lemoine and R. Douville. M. Bertrand and Ph. Ziircher, 

 R. T. Hill, and Ernest Howe should be mentioned. Since work on 

 the Panama Canal was initiated by the United States Government, 

 excluding the investigations associated with official duties, contribu- 

 tions have been made by Franz Toula, A. P. Brown and H. A. 

 Pilsbry, and W. B. Scott. 



In 1911 the Isthmian Canal Commission attached to its staff Dr. 

 Donald F. MacDonald as commission geologist. In October and 

 November, in 1911, I had the privilege of spending a full month in 

 field work along the canal, largely as a guest of the Canal Commis- 

 sion, and I here wish to express to Maj. Gen. Goethals, then Col. 

 Goethals, my very hearty thanks for the facilities afforded me. 

 Doctor MacDonald and I, of course, worked together, and he left 

 nothing undone in making our efforts successful. 



Doctor MacDonald and I both recognized the extraordinary oppor- 

 tunity for making a highly valuable contribution, not only to the 

 geology of Central America, but also to the geologic history of the 

 continents to the north and south. As a result of our conferences, I 

 suggested to the Director of the United States Geological Survey a 

 plan for cooperation between the United States Geological Survey, 

 the Smithsonian Institution, and the Canal Commission. He ap- 

 proved the suggestion and submitted it to the Secretary of the 

 Smithsonian Institution, who also gave his approval. As a result 

 of these preliminaries the following letter was prepared and sent to 

 the chairman of the Canal Commission: 



February 26, 1912. 

 Col. George W. Goethals. 



Chairman Isthmian Canal Commission, 



Washington Office, Washington, D. C. 

 Sir: As a thorough knowledge of the geology of the Panamic Isthmian region is 

 essential to a solution of fundamental problems of the geologic history of both North 

 and South America and of the adjacent oceanic basins; as the excavations for the 

 Panama Canal and along the line of the relocated Panama Bailroad offer opportunities 

 during the next few years never before realized and probably never again to be realized 



