66 ANNALS NEW YORK ACADEMY OF SCIENCES 



account of the fact that the principal occurrence of this type of water is 

 very local, it wonkl l)e possible to combine a study of this kind with a 

 district study such as has been referred to in a preceding paragraph. 



GEOLOGIC HISTORY 



Tlie complete geologic history of the Island of Porto Eico cannot be 

 written until all of these and perhaps other more special investigations 

 have been made. A complete historical statement must be regarded as 

 an end product of the whole range of studies carried out for more special 

 ])urposes. It is, therefore, the final topic and may well be deferred to a 

 time when most of these already suggested have l)een carried far enough 

 so that the data of special importance secured by them are available for 

 this general summary. 



It is evident from tlie appearance of this list that there is a very great 

 amount of geological A\<>i'k iiwaiiiiig tlte investigator in Porto Pico, and 

 that it is \ari('(l and coinplicatf'd enough to riMjuire several years of study 

 in large pari by. experts or specialists in all branches of Ihe su1)ject. It 

 can be seen also that the Island of Porto Eico is a geograpliic unit of 

 more tha.n usual complexity and scientific interest and gives ])roinis(' of 

 results for cH'oi-t ex|)ended in researches along geologic lines. 



Collections 



A beginning has been made toward securing a representative collection 

 of typical rocks and fossils. Several hundred specimens were brought to 

 New York for use in formulating the accompanying description, and as a 

 possible basis for further more special investigations. 



As a first step in this direction, about a hundred thin sections of the 

 rocks have been nuide for microscopic study and detailed comparison. 

 They will form a basis in planning the S])ecial ])etrogra])hic investiga- 

 tions which may l)e undertaken. 



In like manner a large number of fossils have been gathered aiul their 

 general relations are being studied. Additional investigations along 

 paleontologic lines will be in large part outlined or suggested by the trend 

 of these studies, for although the collection is very fragmentary it is 

 nevertheless characteristic and fairly representative of the principal for- 

 mations. 



More than a hundred photographs were taken of strictly geological 

 subjects illustrating typical physiographic features, structural detail of 

 rock formations, structural relations, etc. These are all s,\titably labeled 

 and form the beginning of a collection of illustrations M Poi^tq Rican 



