460 IOWA ACADElMY OF SCIENCE Vol. XXV, 1918 



necessary to purify it by some artificial means. None of the 

 l;rocesses commonly employed — excepting of course distillation 

 — is able to remove such poisonous mineral substances as arsenic 

 and the like. All are aimed at freeing the water from dangerous 

 bacteria. Poisoning by mineral poisons can only affect the man 

 "W'ho actually drinlvs the water, but a case of typhoid fever or 

 eljolera derived from a water may be commmiicated to a large 

 number of others who are susceptible. 



In order to reduce the necessary purification to a minimum 

 the existing water supplies must be protected from further 

 pollution. The curbing of wells may be repaired or built up 

 so that water thrown near the well runs away at once. Good 

 native wells are placarded and put under guard to prevent 

 nuisances in their immediate neighborhood. 



Where the supply is to be taken from a stream, the senior 

 officer is required to designate the point at which the drinking 

 and cooking water is to be taken. Down stream from, that point 

 places are selected for the bathing of men and animals as well 

 as the usual fording back and forth. Considerable pollution of 

 a stream may sometimes occur as a result of the necessity for 

 crossing a river before selecting the source of the supply. Once 

 the source is designated it is protected in the usual manner by 

 .means of notices and guards. 



While good use may frequently be made of the better sort of 

 native wells, the troops will sometimes be faced by the necessity 

 of constructing new ones. Circumstances will dictate whether 

 it is better to construct dug wells, or driven, drilled or bored 

 ones. Driven wells are rapidly put down where the rock is not 

 too hard and do not usually require a great amount of appa- 

 ratus. On the other hand, they do not offer much opportunity 

 for the storage of water. The British army has made use of a 

 variety of the driven well which they called the Norton tuibe 

 well. It was intended to be used by marching troops and for 

 this purpose it was not a success, due chiefly to the amount of 

 time required. It was adapted to loose mantle rock to a depth 

 of only twenty-five feet. It took some time to get the water 

 clear and it was often high in bacteria due to the contamination 

 introduced in driving, for most new wells require some time to 

 get rid of the bacteria introduced in putting them down. As a 

 means of increasing a supply, however, the Norton tube well 

 would have some use where the troops were expected to remain 

 for a time in camp. 



