142 ^^'< Philippine Jounml of Science im 



popular as health resorts. At present only a few springs are 

 much visited. The Insular Government has erected a bath at 

 Sibul SprinjTs, and this place, as well as Los Baiios and Tagsan- 

 jan, has many patrons. The Los Bahos water is carbonated, 

 bottled, and sold. 



Some of the springs are so saline that the recovery of salt 

 from them is an easy and profitable undertaking. A number 

 of springs in Nueva Vizcaya are now so utilized. 



The waters vary widely in quality. The total solids content 

 ranges from 24 to 6,025, and chlorine from 0.7 to 3,120, while 

 the maximum free ammonia content is 6.2. 



WATER SUPPLIES OF MINDORO 



Mindoro, one of the largest of the islands of the Archipelago, 

 is very sparsely populated. It has between 60,000 and 70,000 

 inhabitants, w'ho live near the coast. The interior has been 

 little explored and is uninhabited except for from 6,000 to 7,000 

 uncivilized Mangyans. 



The surface waters in many districts, in addition to being 

 unsafe, are so brackish that they are unpleasant to the taste, 

 and a great deal of trouble has been experienced in providing 

 the people of Mindoro with water. However, in recent years 

 the water supply has been greatly improved by the installation 

 of jet-rig wells by the provincial authorities. 



A brief field trip was made to Mindoro for the purpose of 

 investigating the proposed municipal water supply of Calapan, 

 the provincial capital, but the scope of the investigation was later 

 enlarged to include several other towns. 



Calapan. — Calapan, a town of 9,000 inhabitants, is extremely 

 unfortunate in regard to water supply. The surface wells are 

 brackish, the river is affected by the tides, and good springs are 

 lacking. All attempts to secure a supply of potable water by 

 sinking deep wells have been without success. Limited amounts 

 of brackish water are found at slight depths in drilling opera- 

 tions. Black sand containing sea shells is found underlying the 

 soft coralline formation near the surface, until, at a depth 

 of about 30 meters, a hard rock stratum about 30 centimeters 

 thick is encountered. Penetrating this rock the drill suddenly 

 sinks, and very hot, salty water rises in the drill hole to about 

 ground level. The water from the well at the public market at 

 Calapan showed a temperature of 40° C. Although clear and 

 colorless at first, it became yellow and turbid on standing for a 

 short time, due to the escape of carbon dioxide and the resulting 

 precipitation of calcium and iron salts. 



