g a suitable outlet is a serious
one, and in many cases impossible of solution, so that the householder,
being unable to find an outlet, must put up with the ground water and be
as patient as possible during its prevalence. It does not do to trust
one's eye to find a practicable outlet, since even a trained eye is
easily deceived. An engineer with a level can tell in a few moments
where a proper point of discharge may be found, and it is absurd to
begrudge the small amount which it will cost, in view of the large
expense involved in digging a long trench to no purpose.

Some years ago the writer was able to note the conditions in a house
where the cellar excavation went three feet into limestone rock. The
strata were perfectly level and the cellar floor of natural rock was
apparently all that could be desired, smooth and flat, without involving
any expense for concrete. One wall came where a vertical seam in the
rock existed, and since this natural rock face was smooth and vertical
and just where the cellar wall should go, it seemed unnecessary to dig
it out and lay up masonry in its place. So it was left and the house
built. When the spring rains came, however, the cellar was turned into a
pond, water dripping everywhere from the vertical rock face, and coming
up through the cellar bottom like springs. It cost a great deal more
then to make the changes and improvements necessary in order to secure a
dry cellar than it would have done at the outset. This serves as an
illustration of the need of taking every precaution at the beginning to
insure a dry and well-drained soil around and below the cellar walls.

CHAPTER III

_CONSTRUCTION OF HOUSES AND BARNS WITH REFERENCE TO HEALTHFULNESS_

Any liability to disease that may come from faulty construction of
habitations is likely to spring from a polluted subsoil. Such pollution
vitiates the air drawn from that soil and is a source of danger on
account of the resulting impurity of the whole atmosphere within the
house.

_Shutting out soil air._

We have already seen (Chapter II) how it is possible for soil charged
with organic matter to deliver, either through suction from a heated
house or on account of a rising ground water, soil air into the cellar,
and also that moist air may enter the house in the same way. In order to
prevent this, it is plainly necessary to interpose some air-tight or
water-tight layer between the house and the soil, and also, since
perf