BERKEY, GEOLOGICAL RECONNOISSANCE OF PORTO RICO 7 



still preserved that are now wholly abandoned by the waters that for- 

 merly occupied and helped to form them. There are no inland lakes, but 

 there are a few coastal lakes and they appear to be related to the develop- 

 ment of alluvial plains or playas and recent elevation and subsidence 

 changes. 



The climate is strictly tropical, but it is so tempered by reason of the 

 constant trade wind breezes from the ocean and the elevated character of 

 much of the ground that it is usually agreeable and mild. The lack of 

 great changes of temperature and the prevailingly moist conditions on 

 most of the island have direct influence on the character of the rock decay 

 and disintegration and also on the qualit}^ of the soil produced as well as 

 its behavior as a residuary product. Other matters of climatic conditions 

 have little or no bearing on geological problems and may well be avoided. 

 The average daily temperature is eighty degrees; it rarely goes above 

 ninety degrees or below seventy. The maximum temperature is ninety- 

 nine degrees. Extremes recorded for the year indicate a range of forty 

 degrees. 



The area of Porto Eico is given as 3,670 square miles, which is about 

 three-fourths the size of the State of Connecticut. It is roughly rectan- 

 gular in outline and in actual dimensions is about thirty-five miles in 

 average width, and one hundred and five miles long from east to west. 

 It is the fourth in size of the West India Islands and is one of the most 

 productive and densely populated districts in America. 



Because of the greater interest recently taken in studying the natural 

 ■ resources and natural history of Porto Rico, it was judged to be a suitable 

 time to make a more elaborate and detailed study of the island's geo- 

 logical framework and history. In accord with this view the Xew York 

 Academy of Sciences organized an expedition which spent a part of the 

 summer of 1914 on the island. The accompanying descriptions are based 

 on the work accomplished by this expedition. 



New York Academy of Sciexces Expeditiox 



The geologists sent to make a preliminary study or reconnoissance of 

 the Island of Porto Rico left :N'ew York on the 15th of August, 1914. 

 Four weeks were spent in Porto Rico, the expedition returning to New 

 York City on the 21st of September. The party consisted of Dr. Charles 

 P. Berkey of Columbia University, New York, and Dr. Clarence N. 

 Fenner of the Geophysical Laboratory, "Washington. Arrangements were 

 made with the bureau of transportation of the Insular government in 

 San Juan for conveyances, so that as much ground as possible could be 

 seen in the time available. More than 2,000 kilometers were covered by 



