RURAL ENGINEERING. 587 



The subject matter is presented under the following chapters : Pure water — 

 inorganic constituents of natural waters, animal and vegetable impurities, 

 sources of water supply, distribution, storage, preliminary purification, sand 

 filtration, mechanical filtration, softening of water, sterilization, electrical 

 modes of sterilization, and analysis and interpretation of results. 



Water supplies in the Philippine Islands, A. J. Cox, G. W. Heise, and V. Q. 

 Gana {Philippine Jour. Set., Sect. A, 9 (1914), No. 4, pp. 273-411, pis. 5).— It 

 has been attempted in this paper to classify and arrange the information re- 

 garding the general status of water supplies in the Philippine Islands which 

 has been collected up to date. 



The data first show that " water from surface streams, no matter how well 

 guarded, is not entirely satisfactory, since it is always subject to sudden con- 

 tamination." Analyses of the water from shallow wells showed that nearly 

 every well examined was dangerously poUnted. It is stated that the best natu-' 

 ral potable water is at present furnished by artesian wells. " The high chlorin 

 content is one of the most notable general features of Philippine artesian waters. 

 This does not necessarily indicate sewage pollution, but rather seepage from the 

 ocean or contact with some underground salt deposits or impregnated rocks. 

 The water from some of the artesian wells has been found to be too salty to 

 drink." Flowing wells are deemed preferable because of the decreased danger 

 of pollution, and artesian water has in general been quite satisfactory, both 

 from the chemical and biological points of view. "In many instances where the 

 quality left something to be desired the water was so much better than any 

 other aA-ailable .supply that its use has been permitted." 



Water-borne diseases are said to be more prevalent in the Philippines dur- 

 ing the rainy season than at any other time, due to the wa.shing of accumulated 

 surface debris into the water courses. The three most important water-borne 

 diseases are said to be typhoid, cholera, and entamoebic dysentery. 



Methods for the purification of water supplies discussed are distillation, boil- 

 ing, filtration, and the use of ultraviolet light, copper sulphate, and calcium 

 hypochlorite. Boiling is considered to be the simplest and the most universal 

 safeguard in so far as contamination of water due to living organisms is con- 

 cerned. Tests of the copper sulphate method showed that in order to safeguard 

 the supply against cholera the addition of copper sulphate in the ratio of 1 part 

 per 150.000 parts of water (a strength considered undesirable for drinking pur- 

 poses) acting over a period of four hours would be required. 



Further data report in detail on water supplies for industrial purposes. It 

 is stated that the need of a systematic water survey in the Philippine Islands 

 is strikingly apparent and that " by combining the geologic information with 

 all available chemical and biological data concerning the water occurring in any 

 one district, it should not be diflicult to establish safe limiting values for the 

 normal constituents of water to serve as a basis in determining its fitness for 

 any particular purpose." 



The influence of the forest on the water supply, Henle (Jour. Gasbcleucht., 

 57 (1914), pp. 742-750; abs. in Wasser u. Abivasser, 9 (1914), ^^o. 2, pp. 50, 

 51). — From a critical review of the literature on the subject it is concluded 

 that ground water does not originate solely through seepage of precipitation, 

 but in many cases is formed only by the condensation of water vapor. It is 

 pointed out that the transpiration of rainfall by forests often reaches 400 mm. 

 (about 15.7 in.) annually and that this moisture is returned to the soil in the 

 form of vapor and there condensed. 



The importance of forests with reference to the water supply, K. E. Net 

 (Wasser, 10 (1914), No. 18, pp. 521-524; abs. in Wasser u. Abwasser, 9 (1914), 

 No. 2, p. 51). — The author disagrees with the assumption that the heavy forest- 



