organic matter contained in the wells in the vicinity of Trinity, St. Paul’s, and St. John’s burying grounds, which for more than a century furnished the only water used by those residing in their neighborhood. No one can doubt that the use of such water, as well as that from the wells on the Collect, and over the greater portion of the city below Canal-street, must have proved extremely detrimental to the health of the citizens, and especially to children, and infants. We believe, therefore that the introduction of the Croton water, will increase the average duration of human life in the city of New-York, from 8 to 12 per cent. From 1815 to 1836, it ranged from 30.08 to 22.05, (in 1836), but the mean duration of life for the last 20 years is about 25 years; and the ratio of mortality, according to population, about as 1 to 35. From the manner, however, in which the inspector’s reports have been made, from the imperfection of the law, no great confidence can be placed in the returns,--those carried out of the city for burial, not having been included. From a “Report on the subject of introducing pure and wholesome water into the city of Boston, by L. Baldwin, Esq., Civil Engineer,” it appears that the whole number of wells in that city in 1835, was 2,767. The water from 2,085 of these wells was drinkable, though brackish and hard, and 682 of them were bad and unfit for use. There were only seven of the city wells which yielded soft water occasionally and for washing, and from 33 of them the water was obtained by deep boring. “Within a few years,” says the Report, “it has become common in Boston, and the vicinity, to bore for water, and to make what are called Artesian wells. But no certain or valuable result has grown out of these endeavors. There are 33 bored wells, only two of which are stated as furnishing soft water. The same remarks will apply to the public wells of this city, the most of which produce nothing but hard and brackish water, and none of which is sufficiently soft to authorize its use in washing clothes,” &c. LAKE WATER is a collection of rain, spring and river water, usually more or less contaminated with putrefying organic matter. It is generally _soft_, and when filtered, is as good and wholesome as any other description of waters. Though lake water cannot be characterized as having any invariable qualities; yet most of the Lakes of the United States, especially our great ones, afford a very pure water. In many of our smaller lakes the water is more or less stagnant, and of course very unhealthy. _Marsh Water._ This is analogous to lake water, except that it is altogether stagnant and is more loaded with putrescent matter. The sulphates in sea and other waters are decomposed by putrefying vegetable matter, with the evolution of sulphuretted hydrogen; hence the intolerable stench from marshy and swampy grounds liable to occasional inundations from the sea. Marsh water cannot be drunk with safety either by man or beast.