BERKEY, GEOLOGICAL RECONNOISSANCE OP PORTO RICO 9 



corner of the islainl. o])servations were made on all sides or completely 

 around the unexphjred areas. Because of the extent of the reconnois- 

 sance, it is the opinion of the writer that all of the essential, large, funda- 

 mental geolooical formational units have heen found and their general 

 structural relations have heen determined. 



OBJECT OF THE EXPEDITION" 



The purpose of this expedition was, first of all. to determine the nature 

 and origin of the rock formations of Porto Rico, and to group them into 

 series suitable for use in subsequent geological work. In the second place, 

 it was the object of the party to determine as many of the larger struc- 

 tural relations as could Ije seen and to unravel as much of the geologic 

 history as such a hasty examination would warrant. In the tliird place, 

 the physiographic features Avere studied for the purpose of determining 

 their origin and relation to the formational structure and their bearing 

 on the more recent history of the island. /Lastly, it was appreciated that 

 the island was complex enough to have many problems that could not be 

 solved without very much more extended investigation, and it was the 

 purpose of this expedition to point out the problems that should receive 

 special study and that seemed to give promise of important result^ Con- 

 siderable attention has been given to the economic resources of tlie island 

 by private. individuals and considerable money has ])een spent on various 

 enterprises connected with their development. These problems were also 

 kept in mind, and wherever convenient, special observations were made on 

 them. Although it is possible to make suggestions concerning these eco- 

 nomic resources, they are for the most part matters that should receive 

 very much more extended special study. A matter that concerns the wel- 

 fare of the island more directly than any of these is the question of 

 quality and variety alid origin of the native soils. These of course are in 

 large part geologic matters also, and although this reconnoissance is not 

 sufficiently detailed to form the basis of a discussion of this matter, it is 

 one of the lines of investigation connected with further work that will 

 have direct value. 



Investigations and Discussion 



eock formations 



, The most fundamental thing to l)e determined at the outset of an in- 

 vestigation of this kind is to discover and differentiate the different rock 

 types and the structural units to which they belong. All of the prelimi- 



