INCUBATOR HOUSES AND CELLARS 329 
A building put up expressly for incubation purposes need not 
be very expensive; but a few requirements must be provided 
(Fig. 156, A, B, C, D). The floor should be from four to five feet 
below the level of the ground, and the ceiling from eight to ten 
feet high, giving about five feet below ground and five feet above. 
Double walls, especially above the ground, are essential, as they 
aid materially in keeping the temperature uniform. The subgrade, 
or wall below the ground, is best constructed of poured concrete 
Fig. 156.—Four views showing construction of hollow-tile incubator cellar. A, Forms 
ready for pouring concrete foundation wall; B, forms removed; C, hollow-tile construction 
and manner of framing roof; D, completed cellar. 
or stone (Fig. 81), while the side wall above ground can be made 
of lumber,—2 x 4 inch studding, sheathed inside and out. Or 
_ it can be constructed of hollow tile, which has proved satisfactory, 
-as it is almost a non-conductor of heat. Such a tile, well stuccoed 
inside and out, is economical, durable, easily built, not susceptible 
to temperature and moisture variations, and can be quickly and 
easily cleaned. 
The building should have a loft overhead, to insure uniformity 
of temperature. For this purpose, a two-pitch or gable roof is 
best, and it is advisable to put in heavy ceiling rafters and a solid 
board floor, so that the loft can be used for storage purposes. 
Ventilation.—It is unnecessary to install an expensive ventilat- 
