BERKEY, GEOLOGICAL RECONXOISSANCE OF PORTO RICO 57 



Guano 



Bat guano is found in some of the caves in sufficient amount to be a 

 source of local fertilizer. 



Road Metal 



Several kinds of stone were seen used extensively in road improve- 

 ments. The particular variety used depends largely on the local supply, 

 but the most common are the Arecibo limestone and the massive syenite 

 and granite porphyry. There is no lack of these as well as other types 

 suitable for such use. 



There are other mineral substances that will invite investigation, but 

 no others came under the writer's personal observation and no facts re- 

 garding them are in hand. 



HOT SPKINGS 



Thermal springs are known in the vicinity of Coamo. Judging from 

 their location and apparent relation to other physical features, they are 

 believed to lie along a fault weakness. The district is also one of com- 

 paratively late igneous activity, and this, coupled with the other factors, 

 leads to the suspicion that the springs are directly connected with the 

 dying igneous activity and. may actually represent juvenile waters. 



At Coamo Springs Hotel, one of these springs has been developed and 

 controlled for commercial purposes. The water is hot as it comes out of 

 the side of a small ravine and runs down over the slope, which is covered 

 to a moderate extent with deposit from these waters. The immediate bed 

 rock is not well exposed, but it is judged to be either a tuff or an igneous 

 complex and the field relations in the vicinity show that there is a thick 

 series of beds both above and below. No doubt critical field study could 

 determine the actual relations with considerable certainty. 



An analysis of these waters, furnished by the proprietor of the springs 

 and made at the agricultural experiment station at Mayaguez, is as fol- 

 lows: 



Fixed elements j)er litre of loater 



Free carbonic acid . 01296 



Sulphate of lime 0.79902 



Sulphate of soda 0.52531 



Chloride of potassium . 00031 



Chloride of sodium 0.2.3054 



Silicate of soda 0.08127 



Carbonate of soda , 0.03503 



Carbonate of iron 0.01114 



Total 1.68559 



