vided the level of the ground water allows the construction of such a
cesspool. In any case, it should be at some distance from the house, so
that if it overflows, the water will not seep back to the cellar walls.
By water-proofing the main wall and then backfilling against the wall
with coarse gravel or broken stone, the same results as with open
areaways are obtained and at a much smaller cost.

_Dampness of masonry walls._

One fact peculiar to all kinds of masonry and known to all careful
observers is that stone work, brick work, and concrete will allow
dampness to permeate, whether it comes from water-bearing soil or a
driving rain. One objection to concrete-block houses has been that a
hard rain would cause moisture to form on the inside. Brick buildings
have the same defect when the walls are built solid.

An air-space in the cellar walls is the only way of insuring a dry
cellar, if the bottom of the cellar is below the level of the ground
water. A four-inch course of hollow brick may be used on the inside, or
the wall may be actually divided into two walls with a space between.

[Illustration: FIG. 7.--Wall modes of making air-space.]

Figure 7 (after Warth) shows three different ways by which an air-space
is secured and the two component parts of the wall held together. In the
top view, the two walls, one eight-inch and one four-inch, are held
together by wire ties, leaving an air-space of about four inches. In the
middle drawing the walls are tied together by making the air-space three
inches wide and then lapping the brick laid as headers over both walls.
In the bottom view special terra-cotta blocks are used which pass
through both walls. There can be no question of the value of such
construction in eliminating dampness from the inside wall, but, it must
be admitted, the cost of the walls is increased somewhat.

_Use of tar or asphalt on the wall._

Instead of an open space, nowadays, it is more customary to thoroughly
plaster the outside of the cellar wall, and then paint it with a tar
paint put on hot, which will adhere fairly well to the cement or
masonry. Asphalt cannot be very readily used for this purpose unless it
is an asphalt oil with but little bitumen paste. A paving asphalt, for
example, even applied hot, does not adhere to the masonry, but slides
down the walls as fast as it is applied. A successful method, however,
of using such asphalt is to build the cellar wall in two parts,
separated