232 



University of California. 



[Vol. 2. 



INTRODUCTION. 



Because of the richness of its undeveloped mineral resources, 

 the complexity of the problems presented by its geologic phe- 

 nomena, its comparatively easy accessibility, and its forming a 

 connecting link between the two great divisions of the American 

 continent, the Isthmus of Panama seems destined to be of excep- 

 tional interest to students of geology. During about three months 

 in the early part of the year 1898, the writer was engaged (inci- 

 dental to prospecting for the precious metals) in a somewhat desul- 

 tory investigation' of the geologic history of the central portion of 

 the Isthmian country, traveling about 1,000 miles by schooner, 

 canoe, horseback, and afoot, and although the time was hardly 

 sufficient to gain a very comprehensive knowledge of the subject, 

 it resulted in the discovery and partial exploration of several forma- 

 tions earlier in age than any yet reported from the Isthmus. 



Great obstacles to the pursuit of geological study in such a 

 tropical land as the Isthmus of Panama 'are presented by the 

 density or jungle-like character of the vegetation in large portions 

 of the low plains and in certain high mountainous areas where rain 

 falls at least once during every day in the year; by the enervating 

 effect of the warm moist atmosphere, which dulls the intellect and 

 decreases the power of observation, destroying the zest for knowl- 

 edge, which is the real incentive to scientific progress ; by the 

 scarcity and in portions of the country total absence of roads or 

 even a path or trail ; and by the long delays consequent on life 

 among a people characterized by a lack of energy. In illustration 

 of the first statement, I will mention that one morning I climbed a 

 high tree and from its branches learned more of the geology of the 

 vicinity in ten minutes than I had in the preceding several days of 

 travel in the forest. 



In January, 1895, Mr. Robert T. Hill examined a section across 

 the Isthmus on the line of the Panama railway and canal, and 

 another across Costa Rica between Punta Arenas and Port Limon. 

 The results are given in his admirable paper entitled " The Geo- 

 logical History of the Isthmus of Panama and Portions of Costa 



