EURAL ENGINEERING. 883 



wells were located, and the depths predicted by the operator of the divining 

 rod varied only slightly from the actual depths to water. The operator was the 

 only one who was able to obtain results with the rod, and while the autlior 

 admits that in this case its use was not only successful but economical he 

 expresses some doubt as to the safety of depending in general upon such 

 means for locating M^ater. 



Investigations on the filtration of drinking water.— I, On the theory of 

 slow sand filtration, K. Kisskalt (Ztschr. Hyg. u. Infektionskrank., 80 (1915), 

 No. 1, pp. 57-64, fig- i).— Experiments to determine the cause of the purifying 

 effect of slow sand filtration on water are reported. 



The results indicate that this effect can not be entirely attributed to the 

 mechanical removal of dangerous organisms and contaminating matter by the 

 filter and the surface scum. The use of disinfectants, such as potassium 

 cyanid, which destroy protozoa and do not injure tlie bacteria almost com- 

 pletely destroyed the effect of a filter. It is thought, therefore, that much of the 

 purifying effect of slow sand filtration can be attributed to the protozoa. 



Sterilization of water by chlorin, J. J. H. Nelson {Brit. Med. Joun, No. 

 2836 {1915), pp. 789-793, figs. 2).— The methods and apparatus used for the 

 sterilization of small drinking water supplies by the use of chlorin are de- 

 scribed and experiments with this method using artificially contaminated water 

 and natural water are reported. 



The chlorin was obtained from potassium chlorate and concentrated hydro- 

 chloric acid and was used in the experiments in the strengths of 1 part chlorin 

 solution to about 500,000 parts water. 



It was found that water artificially contaminated with Bacillus typhosus, 

 B. paratyphosus A, and B. cholerce was rendered safe by this treatment after 

 a contact of one-half hour. Natural waters were also successfully treated. 

 The author advocates the use of the chlorin in a strength of, roughly, 1 in 

 500,000 parts of water and states that chlorin used in this strength does not 

 impart any objectionable taste to the water. 



This method is considered to be particularly adapted for domestic use and 

 for camps and troops in the field. An apparatus for domestic use is described 

 and illustrated. 



Purification of drinking water by calcium hypochlorite, H. Vincent and 

 Gaillard (Compt. Rend. Acad. Sci. [Paris], 160 (1915), No. 15, pp. 4S3-4S6). — 

 This article states that calcium hypochlorite is effective, rapid, and safe for the 

 purification of driaking water. Active chlorin to the amount of 3 mg. per liter 

 of water is considered sufficient. This may be given in a mixture of 0.015 gm. 

 of hypochlorite of calcium and 0.08 gm. of pure sodium chlorid. Tlie addition 

 of the sodium chlorid, it is stated, favors the rapid diffusion and dissolution 

 of the active chlorin in the water to be purified. 



Sterilization of drinking' water with chlorid of lime in the field, G. Wesen- 

 BERG (Hyg. Rundschau, 25 (1915), No. 8, pp. 273-286, fig. 1). — Experiments on 

 the sterilization of drinking water in the field are reported. 



It was found that chlorid of lime added in a quantity corresponding to 0.15 

 gm. of active chlorin per liter of water is sufficient to kill infectious organisms 

 within ten minutes. The use of increased quantities of chlorid of lime is rec- 

 ommended for water with a high content of contaminating organic matter, 

 but it is considered necessary in such cases to filter the water before treatment 

 to remove the coarsest matter. The addition of substances setting free hydro- 

 gen peroxid was found to form harmless combinations with the chlorid of 

 lime and to remove any disagreeable taste. The composition of the water, 

 aside from a slight increase in turbidity and hardness, was not influenced by 

 such treatment. 



