Pure water is essential to the health and comfort of every community: there is no argument to the contrary. How such a _desideratum_ can be acquired and maintained is a problem which requires the closest application of science, as well as mechanical and engineering skill. The question, whenever and wherever applied, becomes an isolated reality, and the solution, instead of being based upon established formulas or analogy, is almost wholly dependent upon the individual facts and conditions connected therewith. The aspect of the question a century hence will be very different from what it is to-day, even as in its present bearings it differs from the time when the woodman’s axe was the only sound of industry that echoed through the sleeping valleys and over the watchful hills of New Hampshire. In that day the hardy pioneer quenched his thirst by the side of any stream or spring with water as pure as earth could give. He thought not to glance up the stream to see if it was spanned by a family vault, or flanked by a barn-yard. Likewise, if he partook from the bubbling spring or the primitive well, he never imagined a crystal of urea came up in the tiny fountains of sand at its bottom, or that the sparkle of the water was the carbonic acid of a sink drain; for around him were no such dangers. But civilization (in many respects a misnomer) came on, and brought with her more evils than one,—seduced the virginity of nature, and begot a host of illegitimate products and conditions. Into her very veins—the streams and rivers—have been injected the effete products of waste and decay; and to-day her very gifts, poisoned by men, bring pain, poverty, tears, and death into many households. We have all, no doubt, traced some cases of the zymotic order to polluted water, with evidence that left no doubt as to the correctness of our conclusions. As to how far such influences extend in the causation of disease is undetermined, but I believe it extends far beyond the category of acute zymotic diseases.