River-water for daily use of course requires a system of pipes, and in small places is practically unavailable; so that wells are likely, in such case, to be the chief source of supply.

Such water will of course be spring-water, with the characteristics of the soil through which it rises.

If the well be shallow, and fed by surface springs, all impurities of the soil will be found in it; and thus to _dig deep_ becomes essential, for many reasons.

Dr.Parker of England, in some papers on practical hygiene, gives a clear and easily understood statement of some causes affecting the purity of well-water.
"A well drains an extent of ground around it, in the shape of an inverted cone, which is in proportion to its own depth and the looseness of the soil.

In very loose soils a well of sixty or eighty feet will drain a large area, perhaps as much as two hundred feet in diameter, or even more; but the exact amount is not, as far as I know, precisely determined.
"Certain trades pour their refuse water into rivers, gas-works; slaughter-houses; tripe-houses; size, horn, and isinglass manufactories; wash-houses, starch-works, and calico-printers, and many others.