62 AXXALS XEW YORK ACADEMY OF SCIEXCES 



on a scale of approTimatelY f inch per mile which has even the kilometer 

 distances along the roads indicated. TTiitil some sort of a contour map 

 c^n be secured, such maps as these will be found eminently serviceable. 

 Along the south coastal margin within the region of irrigation devel- 

 opments, there has been some special mapping with contours. In no case 

 do they cover much ground beyond the outer lowland and terrace border, 

 and because of this limitation they are not so generally useful for our 

 purpose as the Interior Department maps. They are. however, very 

 much more accurate and detailed and for the territory covered are emi- 

 nently suitable as base maps. 



GEOLOGIC 3IAP 



A geologic map of the island should be one of the results of this series 

 of studies, whether a relief map is secured or not. Such a map of the 

 whole island is necessarily an ultimate rather than an immediate product, 

 but district maps can be undertaken at once, with no difficulty whatever. 

 These preli min ary districts can be selected so as to include some of the 

 most promising investigation problems in special lines, and both kinds of 

 work can thus be carried on at the same time. This therefore leads 

 directly to the next item, which is district studies. 



The only geologic map thus far attempted is that by E. T. Hill. 



DISTRICT STI7DIES 



It is possible now to select areas which are known to contain geologic 

 features of special interest and significance, and it will generally be con- 

 venient, if not indeed necessary, for the investigator to make a detailed 

 geologic map as a secure foundation for his special studies. One of these 

 is the Coamo Springs District, which may be made large enough to ex- 

 tend from the Descalabrado river on the west, to Salinas on the east, and 

 reach as far north as Aibonito. It will include as features of special 

 importance for investigation, in addition to the mapping, the hot springs, 

 the great conglomerate series, one of the later of the great volcanic vent 

 complexes, the genetic history and horizon of the Coamo limestone which 

 is a striking mixture of volcanic and organic matters, the high floodplain 

 deposits of the stream valleys and their bearing on late geologic history, 

 and certain physiographic studies connected with the coastal terraces. 

 This district promises, as can be seen, an unusually large range of topics 

 inviting special study, all of which will be illuminating to further devel- 

 opment of the geologic survey of the island. 



Another district of equal promise in a very different manner is on the 

 north coast extending from the Quebradillas to the Arecibo river and 



