Thousands of these wells still abound about the country, where health questions have not received the amount of attention they deserve; and notwithstanding that years may have passed, and no harm have come from them, a day may come - and every year the increase of the population renders its advent more likely - when the soil, which has done its work so long and so well, refuses to do it any longer, and the water will become a drink of death, and a carrier of disease. These receptacles, for the most part, favor the increase of animalcules and fungoid growths and the generation of impure gases, and this contamination is further helped, in many places, by the unaccountable practice of placing the cistern for drinking and other purposes directly over the water-closet. The capacity of water, exposed to an impure and noxious atmosphere, for absorbing impure matter, has been forcibly illustrated by Dr. Lyon Playfair, who mentions an instance in point: "One of my assistants," he says, "was making experiments with an oil which had the smell of the concentrated urine of the male cat. The smell was insufferably offensive, and was so readily absorbed that it was impossible to drink-the water placed in the room. Every vessel containing a liquid in the room soon became contaminated with this horrible smell". The exposure of the water stored in cisterns and water-butts to the atmosphere is another source of impurity, by the absorption of impure gases from the air. The atmosphere of any large place is the receptacle for the exhalations of many inhabitants, and of thousands of animals, dead and living, of stable-yards, privies, dung-heaps, slaughter-houses, and of the vapors from dustbins and gas-works, and like establishments. Even when water is taken into the close, heated, and offensive rooms of the poor, it rapidly absorbs the offensive gases with which the air of the rooms is loaded, and becomes tainted. "When water," says Dr. Hector Gavin, "has been preserved in butts or tubs outside, exposed to the foetid atmosphere of a privy, it taints rapidly, and it is almost impossible in calling for a tumbler of water in the houses of the poor to find it free from a mawkish taste".

We see now, how, at every turn, there are impurities in the water supplied to us by companies, and more especially the water we ourselves derive from wells, to be got rid of. First of all, there are impurities of a harmless although objectionable nature, such as living organisms and certain inorganic suspended impurities, which render the water turbid and of a disagreeable appearance. And, secondly, there are organic impurities of a most harmful nature, which may be the cause of serious danger to health and life. Although these latter may not be present in the actual source of supply, they may find entrance through dirty vessels and careless storage. The question, therefore, is an important one: What means can be adopted to reduce to a minimum the chances of accident arising from drinking impure water?

And to this question there is but one answer, viz.:- The adoption of a system of purification.

Dr. Charles Smart, in his paper on "Water Supply of Cities," read before the Sanitary Congress, very justly declared that chemical tests alone are not conclusive evidence of the wholesomeness of a public water supply, in the face of an excessive mortality from disease like typhoid fevers, which are largely traceable to a polluted drinking water.

Furthermore, to quote the last annual report of the New York State Board of Health: "It is a thing of common experience that water highly contaminated, even with excremental matter, may be drunk for a long time with apparent impunity by many people; but that at some unexpected moment, either from an as yet unknown change in the fermentation process, or, as is often probable, from the introduction of an almost inappreciable quantity of specific infective excreta, an outbreak of typhoid may devastate the community thus supplied". A distinguished sanitarian tells us, that the effect of impure water is not always sudden, violent or general. On the contrary, its results are more usually so gradual as to often elude ordinary observation, but are not the less real on that account.

The extent and manner in which a public supply is liable, under the best conditions, to be contaminated, is aptly illustrated in the case of New York city. In purity, color and wholesomeness, the Croton ranks second to no other potable water; yet a recent official report by the New York health authorities states that the Croton-water shed embraces 239 square miles, and has a population of 20,000, with 1,879 dwellings, besides barns, pig-pens, cesspools, cemeteries, slaughter-houses and other sources of contamination, and with no drainage, excepting on the surface.

Yet, in comparison to the water supply of many other American cities, the Croton is purity itself. Philadelphia draws its chief supply from the Schuylkill, a sewer and factory-polluted stream. The 300,000 inhabitants of Newark and Jersey City pump into their reservoirs the waters of the Passaic river, filled with the sewage of Paterson. Prof. Leeds says: "The river immediately below the town is black with dye-stuffs, the fish carried over the great falls are immediately poisoned, and analysis reveals that the water has acquired an enormous percentage of nitrogenous matter". Boston's supply is threatened, while Chicago, St. Louis, Cincinnati, Providence, Baltimore, and a score of other cities are drinking water contaminated in the same way by sewage, factory or surface drainage, or by cesspool seepage, into wells. The large majority of rural and village residents depend upon shallow wells dug in porous soil close to leaching cesspools, and the cool draught from the "Old Oaken Bucket" too often contains concentrated poison.