28 Report on Miscellaneous Implements at Shrewsbury, ^c. 
As regards ventilation : — air penetrates into the egg-drawer through holes 
bored in the bottom of the wooden casing at l and in the false bottom, and 
is evenly distributed throughout the egg-drawer. The shape of the bottom 
of the tank, besides aiding the working of the thermostatic band, also serves 
to equalise the heat all over the drawer, so that changing the position of 
the eggs is quite unnecessary. The lamp kept always burning to heat the 
circulating boiler is fitted in a metal chimney, which closely encircles the 
boiler. At the bottom is fixed a broad convex collar s, pierced so as just 
to allow space for the flame, letting as little air up through this aperture as 
possible. This collar extends beyond the chimney, forming a flange outside, 
and forcing the air through the small holes in the lamp below the wick, 
aiding a perfect combustion and making a clear steady flame, independent 
of draughts, and burning without any smell. 
Both the lamp fixed on at the side (or back) and the lever and valve on 
the top of the incubator are protected by metal screens or covers E and I.* 
A thermometer N, to show the temperature over the eggs, is fixed on the 
front of the drawer. A second thermometer serves as an index of the heat 
of the water at the bottom of the water tank, through the tube g. 
The necessary moisture for the eggs is provided by the vessel T, which fits 
round and underneath the egg-drawer. The space between the sides of this 
water vessel is covered by coarse canvas, the ends dipping into the water 
all round. By capillary attraction the canvas is thus kept wet, and the 
incoming air as it passes through it absorbs the necessary degree of moisture. 
A piece of felt or flannel is placed on the false bottom on which the eggs 
rest. 
Bules of Working. — 1. The machine unpacked, stand in its place, leaving 
a foot to two feet of clear space all round and under it. Screw on the boiler 
and chimney as tight as possible with the fingers, and button on the lamp 
screen. If after filling with water the brass unions drip, proceed cautiously 
to tighten them with a spanner, but on no account use any violence, or 
serious damage may be done. 
2. Turn the set screw (or head screw) D as high as it will go, or, better 
still, remove it temporarily altogether. 
3. Fill the tank with boiling water, or with colder water if more con- 
venient. For a 100-egg machine, seven gallons will be required. Light the 
lamp, turning up the flame to its full power, until the machine gets heated 
through. 
4. Leave it like this for some hours, or all night, the valve a being down. 
Fill the water tray. 
5. If boiling water has been used, after a few hours the heat in the drawer 
will be found about 108° or 110°. If cold water be used, it will be necessary 
to keep the valve down until the lamp has raised the heat of the water 
sufficiently to produce a temperature of 108° or 110° in the egg-drawer. 
6. Put the set screw D on and oj^n the valve wide, letting off the heat 
until it is down to 102° or .so. Then, by means of the set screw, adjust the 
valve so that it just touches the ajwrture. Ascertain now, by means of the 
long glass thermometer, the heat of the water at the bottom of the tank a, 
which for a 100-egg size generally requires to be kept about 170°. Record 
these on the register. 
7. Leave for an hour, then look at drawer thermometer, and dip the other 
one carefully to the bottom of the pipe o, to see the heat of the water. The 
drawer heat will now be a degree or two higher, and the eggs can be put in. 
8. The regulation will now go on of itself. Suppose you wish for a higher 
temperature in the egg-drawer, lower the valve (by turning the set-screw) 
* Except in the small-sized mctnl-casod Incubators. 
