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Special precaution should be used to make tight the top and sides of the well so that the water will filter through as great a thickness of material as possible before finding its way into the well. This condition can be secured by laying up a brick or stone wall in hydraulic cement from near the bottom of the well to about a foot above the surface. Care should be taken that any open space between the sides of the well and the brick wall is filled at the bottom with cement and sand or clay, and that it is carefully covered at the top with heavy boards and otherwise made tight. Apparent cleanliness and purity should not be assumed to guarantee absolute freedom from contamination.

The location and surroundings of a well must always be looked after. Very frequently disease germs lurk unsuspected in what is seemingly to the eye the clearest and purest water. The writer regrets that he can not here give a large number of analyses to show the organic matter in water from wells of different locations, but it was almost impossible, owing to the conditions under which the work was carried on, to make the organic determinations, even in those wells which were given an approximate mineral analysis, since search for organic matter must be made very promptly after the collection of the samples, which was impossible in these cases. However, the mineral analyses were made and careful observations were taken regarding the location, elevation, and various surrounding conditions, and the effects of these conditions may be seen in a way by reference to the following table of analyses. An examination of these analyses and of the record of the field tests shows that in a very large proportion of cases the water obtained from wells located on low lands is poorer than that from those on high lands. In most cases where there had been sickness caused possibly by the water, the wells used were situated in low places or near stables or cesspools.

Table showing salts and mineral matter in water of wells

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(1) Estimated as equivalent to sodium chloride.

(2) Equivalent to carbonates and sulphates of lime and magnesia.

Near barn, low

(3) Lime, magnesia and alkalies estimated as equivalent to sodium carbonate. With the true alkalies was estimated all, or a part of the carbonate of lime and magnesia.

The number of wells located near barnyards and supplying water for household purposes was astonishing. Were it not for the remarkably healthful climate and for the out-of-door occupation and good resisting power of those habitually using such water there would be a larger amount of sickness. Water obtained from wells in low places and where the water rests in blue clay was nearly always found to be stronger in alkalies, salts, and sulphuretted hydrogen or soluble sulphides and of inferior quality to that from wells located on higher sand or gravel ridges. Very few of the wells of this district are walled up with brick or stone. Wooden planks are generally used, simply to keep the well from caving in. Some wells are not even planked up. The top is usually very poorly covered and many are kept quite open.

It must not be understood from the above statements that the water of this region is naturally dangerous, for this is not the case. There is, however, great room for improvement in sanitary conditions within the control of man. The following points are suggested as possible aids in bringing about an improvement in the quality of water used for household purposes in this region.

Locate the well on high land, and whenever possible let it be in a sand ridge, or at least in a location which there is reason to believe is underlaid with such material. This will not be very difficult to accomplish in the case of most of the wells in this district. Investigation goes to show beyond a doubt that in most cases the best water is obtained when the well is put through

much sand and gravel, at least for a portion of its depth. This fact of course is generally recognized. Sand and gravel act as a filtering bed, and are often used for the improvement of otherwise impure supplies. Many cities use sand filtering beds with remarkably good results. In the East one of the most thoroughly tested systems of this kind is the comparatively simple sand-bed arrangement of the city of Lawrence, Mass., by which the water is purified for domestic use. In North Dakota a similar system is used at Grand Forks with gratifying results. Usually the organic impurities in the water after filtration amount to but a small fraction of that found in the unfiltered water. Wherever water is found which passes through layers of sand and gravel, as is commonly the case in this part of the state, it will have been subjected to a natural filtration which, as the analyses given in this report show, results in a marked improvement in its quality.

Wells should be located on high land to prevent contamination from the slow percolation of impure surface water; wells in low places naturally receive the sewage and general drainage from the higher portions of land; but high and rolling land favors a rapid run-off of surface water and so usually prevents the introduction of surface impurities.

For obvious reasons it is imperative that wells to supply drinking water should not be stopped at too shallow a depth. Many wells may be found which are little more than mere basins dug a few feet in the soil and sub-soil. The water thus obtained is all from the immediate surface and is very liable to contamination. Wells dug for domestic use should be walled up with brick or stone and not with wood, since the latter does not keep out surface water but furnishes favorable conditions for the accumulation and growth of organic matter; the wood soon begins to decay, thus supplying impurity, while the cracks and rotten places in the wood allow access to small animals.

Based upon the principles mentioned, there are many ways of constructing wells which will furnish pure water and be entirely satisfactory.

The accompanying illustration, Figure 21, is given as a suggestion of one safe method of construction. This will be found applicable in many places in this region but will need to be

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modified often times to meet the local conditions. This plan is intended only for localities where the water will rise by its own pressure at the lowest stages to a point above the top of the inflow pipes marked A, in Figure 21. Wherever the water does not rise of its own pressure so as to overflow these inlet pipes this design for a well would not be available as the pump could. only lift the water out of the well when it rises above the in-take pipe to the pump. The well is dug to within a few feet of the sand which contains the water and which is capped by compact clay or shale. Through this clay or shale the iron tubes, A, are driven, or, if the shale or clay is too hard, the tubes are placed in holes drilled through. All of these tubes, six or eight in number, pass into the water-bearing sand, as seen by the central tube. Each tube is provided with an ordinary pointed cap for the lower end and is perforated along the sides for some distance. The bottom of the well is then cemented very carefully around the pipes, and the entire bottom, D, is covered with a thickness of about a foot with a fine concrete made of Portland' or other good hydraulic cement. Upon this the brick wall is laid in hydraulic cement mortar to about one foot above the surface, and is provided with a tight fitting cover. The tube, C, is placed in the cover to allow a free circulation of air. It should be provided with a fine screen on top or a perforated cap and sides. The tube, B, ending in a perforated cap, is the suction tube leading to the pump. A well constructed in this manner is a great improvement over the one of common construction, since it permits no foreign matter to enter the well and does not require that the water shall stand in the blue clay or shale and thus increase the amount of alkalies as well as of other mineral matter. Whenever it is desired to clean the well the tops of the tubes, A, can be plugged up and the water drawn out. When there is doubt about the water rising, at its lowest stage, to a sufficient height above the inflow pipes, A, to insure a good supply, some slight modifications may be adopted. For example, the bottom of the well should be carried down very near to the waterbearing stratum. When it is evident that the water will rise some distance above the bottom one large in-take pipe A, or several smaller ones may be put down well into the water-bearing stratum. The concrete can then be placed above these in the way illustrated or the pump may be connected directly by means of pipe B, to the one or more pipes sunken into the water-bearing

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