19161 RURAL ENGINEERING. 187 



ft. deep in the axis also yield salt water. . . . The very deep waters of the 

 east side and of the axis increase northward in mineral content, but the shal- 

 low watei's show no such general relation." 



Radio-activity of spring water, R. R. Ramsey (Proc. Ind. Acad. Sd., 1914, 

 pp. 453-469, pgs. 7). — This is a description of methods and apparatus used in 

 the determination of radio-activity in water. See also a previous report by the 

 author (E. S. R., 34, p. 332). 



Water supplies to rural and small urban areas, W. G. Savage {Jour. Roy. 

 Sanit. luat., 36 {1915), No. 9, pp. 365-381).— The author deals more especially 

 with the sanitary side of small water supplies, calling attention to the results of 

 his rather extended experience in judging the purity of water supplies, shallow 

 wells in particular. 



" It is evident that two distinct sources of pollution have to be guarded 

 against — one the local contamination of the specific surface well, and the other 

 the general contamination of the subsoil water. ... If all surface wells were 

 properly lined and made impervious to water for a depth of at least 12 ft., 

 and were covered in to prevent pollution through the mouths of the wells, this 

 would furnish a protection to the water quite sufficient for most country vil- 

 lages, unless the soil was very unsuitable for filtration purposes. . . . 



" One common and widely held error is that a single water analysis, unforti- 

 fied by local investigation, will enable an opinion to be given as to whether a 

 supply is a pure one and fit for drinking purposes. . . . Water analyses only 

 enable an opinion to be formed as to the condition of the sample submitted, and 

 do not justify an opinion which covers the future purity of the supply. . . . 

 The only satisfactory procedure is ... to carefully examine the existing wells 

 and any other sources of water supply, noting the accessibility, the depth of 

 the subsoil water, its direction of flow (if possible), the relationship of the wells 

 to the sources of contamination in their vicinity, the construction of the wells 

 and how far they are built to keep out contaminating matters, the nature of the 

 soil in which they are dug, the liability to flooding, the sufficiency of the water, 

 and when liable to run out, etc. When this has been carried out, the wells 

 which are best protected and from their surroundings least liable to contamina- 

 tion should be critically considered, and samples from these submitted for 

 analysis to ascertain how far the subsoil water itself is polluted. With these 

 some half-dozen samples should be sent for analysis from wells representing 

 the average and worst conditions found from the topographical inspection." 



Well waters from the trap area of western India, H. H. Mann {Dept. Agr. 

 Bombay Bui. 14 {1915), pp. 66, pi. 1). — Analyses of a large number of samples 

 of the well waters from different parts of the district are reported and dis- 

 cussed, with special reference to their uses for irrigation and domestic purposes. 



A simple colloid-chemical process for removing' micro-organisms from, 

 surface water in relation to drinking-water supplies in the field, M. Strell 

 {Munchen. Med. Wchnschr., 62 {1915), No. 34, pp. 1158, 1159, fig. 1; abs. in 

 Chem. Abs., 9 {1915), No. 23, p. 3313). — In this process, a black, doughy mass 

 called humin, giving a colloidal solution with water and prepared from brown 

 coal by treatment with hot sodium hydroxid, is added to polluted water and 

 the mixture is treated with the solution of a metal salt, forming a fiocculent 

 precipitate containing finely suspended substances like micro-organisms, dyes, 

 native proteins, ec. 



In experiments, river water containing 84,9G0 bacteria per cubic centimeter 

 was treated with 10 per cent humin solution at the rate of 5 cc. per liter of 

 water, and the mixture then received 10 per cent aluminum sulphate solution 

 at the rate of 2.5 cc. per liter After sedimentation and filtration the filtrate was 



47580°— 16 7 



