neat cement
should always be put on with a broom or a whitewash brush, mixing the
neat cement with water in a pail, and it does no harm to go over the
surface three or four times, the object being to thoroughly close the
pores in the concrete.

For floors of cellars or barns, the dirt should be evened off and tamped
and then the cement concrete should be spread evenly over it, and tamped
just enough to bring the water to the surface. When partially dry, a
better finish is obtained by lightly troweling the concrete. In a cellar
or barn, it is not necessary to divide up the area into squares or
blocks as is done with sidewalk work, but the entire area may be laid in
one piece. In order to keep the surface level, however, it may be found
convenient to lay down pieces of 2" x 4" scantling, the tops of which
shall be on the desired level of the finished floor. By filling in
behind these scantlings, which can be moved ahead as the filling
progresses, the exact level desired can be obtained. Usually four inches
thick will be a proper depth of concrete for this purpose.

CHAPTER IV

_VENTILATION_

The average individual breathes in and out about eighteen times a
minute, taking into his lungs the air surrounding him at the time and
expelling air so modified as to contain large amounts of carbonic acid,
organic vapor, and other waste products of the lungs. The volume of air
taken in is about the same quantity as that expelled and amounts to
eighteen cubic feet per hour. Fortunately, the air expired at a breath
is at once rapidly diffused throughout the surrounding atmosphere, so
that, even if no fresh air were introduced, the second breath inhaled
would not be very different from the first. But after a certain length
of time the air becomes so saturated with the waste products of the
lungs that it is no longer fit to breathe, and it is evident that in
order to keep the air in a room so that it can be taken into the lungs
with any reasonable degree of comfort, there must be a continual supply
of fresh air admitted with a proper provision for discharging polluted
air. If this is not done, there is, so far as the lungs are concerned, a
process established similar to that which is occasionally found when a
village takes its water-supply from a pond and discharges its sewage
into the same pond.

Not long ago, the writer found in the Adirondacks a hotel built on the
side of a small lake which pumped its water-supply from