VIII. B, 6 Barber: Examination of Artesian Wells 457 



Although some of these colonies resemble colon bacteria in 

 some respects, it is evident that they vary somewhat from typical 

 Bacterium coli. 



From a comparison of the results obtained from the flowing 

 and the pumping wells, it is evident that the pumping wells show 

 a somewhat lower grade of bacterial purity. The best pumping 

 well shows a greater degree of bacterial contamination than the 

 poorest flowing well. It does not seem likely that the majority 

 of the bacteria found in the pumping wells come from the deep 

 water-bearing strata into which the wells are sunk, since flowing 

 wells, in some cases only a few hundred yards away, show a much 

 higher degree of purity ; and it does not seem probable that there 

 is seepage of surface water into these deep strata, since, in the 

 two intermittently flowing wells, at least, there is pressure enough 

 to bring the water near the surface. Neither is it probable that 

 the source of contamination is in the pump. The Fort William 

 McKinley pump, operated by machinery, raises about 600,000 

 gallons daily, and it is unlikely that such a volume of water 

 would be much contaminated in passing through a pump with 

 the ordinary protection from contamination. The waters of 

 Alabang No. 1 and Alabang No. 2 are also raised by machinery, 

 and the sample from No. 1 was taken from the pipe before it 

 reached the collecting reservoir. These three wells showed about 

 the same degree of contamination as those in which a hand pump 

 was used. 



All things considered, it seems probable that the source of 

 contamination is water entering the wells above the deeper 

 strata. In a flowing well, pressure is outward, and, obviously, 

 there could be no inflow of water above the source, unless from 

 strata in which the water is also under pressure. When the 

 water in the well falls somewhat below the surface of the ground, 

 as is the case in the pumping wells, the direction of the pressure 

 in the upper part of the well, at least, is reversed and water 

 may enter at any permeable point. The comparatively low 

 degree of contamination in the pumping wells would indicate 

 that such contaminating water enters in small quantities or is 

 partially filtered before gaining access to the well. 



It is improbable that any of the bacteria occurring in the 

 pumping wells at the time of examination are dangerous to 

 health. Fort William McKinley water is used unboiled by several 

 thousand people, and there is no evidence that water-borne 

 diseases come from its use. It is, of course, possible that some 

 of these wells might become sources of disease under conditions 

 other than those prevailing at the time of examination. 



122778 4 



