IX, A, 4 Cox et al. : Water Supplies in the Philippines 339 



The high chlorine content is one of the most notable general 

 features of Philippine artesian waters. This does not neces- 

 sarily indicate sewage pollution, but rather seepage from the 

 ocean or contact with some underground salt deposits or im- 

 pregnated rocks. The water from some of the artesian wells 

 has been found to be too salty to drink. 



The high free ammonia content of certain wells, as for exam- 

 ple those in the towns of Iloilo, Santa Barbara, and Jaro, Iloilo 

 Province, is especially interesting. These wells are from 60 to 

 175 meters deep, and are cased to the bottom. They probably 

 owe their abnormal ammonia content to the peculiar nature of 

 the strata through which they pass. According to W. E. Pratt 

 of the Bureau of Science : 



The wells at Iloilo are sunk through estuarine deposits which are 

 high in organic matter resulting both from plant and animal remains 

 in the sediments themselves and from included remains of organisms 

 that lived in the salt or brackish water in which the beds were laid down. 

 The character of the water itself is likewise transmitted to the sediments 

 through saturation during deposition and preservation by subsequently 

 deposited overlying strata. Silts with considerable contents of humus, 

 soils, carbonaceous clays, shales, and sands impregnated with salts from 

 sea water are the prominent members of the formation. Artesian water 

 is obtained from lenses of sand or fine gravel in the general formation. 

 It is uniformly salt in the low-lying part of the province at a depth greater 

 than approximately 165 meters. 



A flowing well is to be preferred because of the decreased 

 danger of pollution. It is an established fact that bacteria 

 cannot be entirely removed from deep wells by pumping; on the 

 other hand, flowing artesian wells from deep strata are practi- 

 cally sterile. The pressure in flowing wells tends to prevent sur- 

 face seepage. In a study covering 22 flowing and 12 pumping 

 artesian wells. Barber ^° of the Bureau of Science found that 

 the best pumping well showed more bacteria per cubic centimeter 

 than did the poorest flowing well reported. He says in con- 

 clusion : 



the waters from the flowing wells show a remarkably high degree of 

 bacterial purity and may be regarded as free from pollution by pathogenic 

 bacteria. The pumping wells show a much lower degree of bacterial purity, 

 although it is unlikely that any of them were polluted to a dangerous 

 degree at the time of examination. These wells should be examined oc- 

 casionally — especially during the prevalence of water-borne diseases — 

 since they cannot be regarded as absolutely safe from pollution. 



In general, artesian water has been found quite satisfactory, 

 both from the chemical and biological points of view, and in 



" This Journal, Sec. B (1913), 8, 458. 



