470 IOWA ACADEMY OF SCIENCE Vol. XXV, 1918 



in depth. It is slung from a folding ring. Near the bottom are 

 five self-closing faucets which are small enough to fit inside the 

 neck of a canteen. It weighs about seven and a half pounds 

 when empty and is intended to ibe carried by one of the men. 

 "When filled the weight is about 330 pounds. The chemical ac- 

 tually used is bleaching powder, Avhich is put up in sealed glass 

 tu'bes, containing fourteen or fifteen grains. A package (7^2 

 inches x 3i/^ inches x 414 inches) containing sixty of the tuibes 

 weighs ten ounces. To treat a bag of water, one of these tubes is 

 broken at the file mark it carries, and the contents mixed in a 

 cup of water. The mixture is put into the bag which is then 

 filled. In half an hour the water is ready for use. If the raw 

 water is turbid, it is strained through a filter cloth or blanket. 

 This of course will not remove fine turbidity. Comprehensive 

 experiments have demonstrated that typical and dysentery bac- 

 teria, active amoebae, ciliates and the like are killed within 15 

 minutes. According to Hurst (6) chlorination as usually prac- 

 ticed does not destroy encysted amoebae. 



SUMMARY. 



1) Experience has showTi that careful control of the drinking 

 water supplied is essential to the health of the troops. The con- 

 trol measures include protection of existing supplies, develop- 

 ment of new ones, inspection of all questionable sources and the 

 purification of all contaminated or suspected supplies. 



2) In the present conflict it is necessary to know whether or 

 not a well has ibeen deliberately poisoned as well as to know 

 whether it is polluted with sewage-like material or decomposing 

 animal matter. 



3 ) The bacterial purification of water is 'best accomplished by 

 heat or chemical disinfection, preceded, if necessary, by a pre- 

 liminary clarification. 



4) In spite of the possibility of unpleasant tastes and odors 

 the chlorine compounds are the most satisfactory — as well as the 

 cheapest means of treating water when heat is not practicable. 



5) Bacterial multiplication in sterilized water is rapid in 

 case of re-infection. Care should be taken to avoid dipping into 

 the water with unclean vessels or allowing dust to blow into the 

 container. 



