a depth of
six feet. One of these beds is cultivated with some crop like Italian
rye-grass, which bears copious irrigation; and the other by some crop
like wheat, which, in the absence of irrigation, will thrive on the
fertility left over from the previous season. The volume of sewage is
very great, but the action of the six feet of earth in removing its
impurities seems to be complete; the water flowing out from the drains
having been proved by analysis to be really far purer than the standard
fixed by the Rivers Pollution Commission.

It is an important condition of this system that the sewage, where its
quantity is small, shall be stored in tanks until a large volume has
accumulated, and that it then be rapidly discharged over the soil. There
is no objection to an actual saturation of the ground, provided the soil
is not of such a retentive character as to be liable to become puddled,
and so made impervious. The tanks being emptied, the flow ceases until
they are again filled. During the interval, the liquid settles away in
the soil, by which its impurities are removed. Its descent is followed
by the entrance of fresh air, and the oxidizing action of this,
accompanied during the growing season by the purifying effect of the
growing crop, leads to an entire decomposition or destruction of all
organic matters.

The third system--the distribution of sewage through irrigation-pipes
laid at a depth of ten or twelve inches below the surface of the
ground--has its efficiency attested by numerous instances in private
grounds. I have adopted this system for disposing of the sewage of the
village of Lenox, Mass., where there was no other means available short
of cutting an outlet, at great expense, through a considerable
elevation. This method is an extremely simple one, and is available in
every instance where even a small area of land lying slightly below the
level of the outlet is to be commanded. The arrangement of the
sub-irrigation pipes is easily made: Suppose that in land having an
inclination of about one in two hundred, occupied by grass or other
growth, a trench be dug twelve inches deep, that there be laid upon the
bottom of this trench a narrow strip of plank to insure a uniform grade,
and that upon this plank is laid a line of common agricultural
land-drain tiles, say two inches in diameter. However carefully these
tiles may be placed, there will be at their joints a sufficient space
for the leaking out of any