shown at G, Fig. 16, and arranged to slide to and fro in the
grooved runners H, which makes it possible to have white light, as
at I, or red light as at K, Fig. 16. The white glass with runners
in position is shown at L in the same drawing, but not the red
glass and frame. Ventilation is arranged for by boring a series of
holes near the floor, as at M, Fig. 6, and near the roof as at N
in the same drawing, and trapping the light without stopping the
passage of air, as shown in the sections, Fig. 17.

The finish of the roof at the gables is shown in Fig. 18, the
strip under the boards holding the felt in position when folded
under, and the same is true of the roll at the top of the roof in
Fig. 19.

The house will be much strengthened if strips, as shown in Fig.
20, are fastened in the corners inside, after lining with brown
paper, screwing them each way into the boards. The door may have a
latch or lock with a knob, but should in addition have two buttons
on the inside, fixed so as to pull it shut tightly at top and
bottom. A waste pipe should be attached to the sink and arranged
to discharge through the floor. A cistern with pipe and tap can be
fastened in the top of the dark room, if desired, or the room may
be made with a flat roof, and a tank stand on it, though this is
hardly advisable.

It is absolutely necessary that the room be well painted, four
coats at first is not too many, and one coat twice a year will
keep it in good condition.

A brick foundation should be laid so that no part of the room