54 
The Illustrated Bools of Poultry. 
mo\ es freely at the outer end. Above, the free end of the lever is connected by a rod, R, 
with a valve, P, and below by a spiral spring, V, with the lamp G. When, therefore, the piston 
is raised, the valve P opens, and warm air rushes out to reduce the temperature ; while Q is 
a slide at the bottom of the machine to lower it still faster if necessary. At the same time 
this is being done, the lamp-flame is being lowered by other mechanism. All these parts are 
duplicate, there being a precisely similar lamp, boiler, valve, and other contrivances at 
each end ot the apparatus, one ot the tubes of alcohol communicating with each ; and these 
two sets of heating and regulating apparatus to some extent correct and compensate any 
sudden irregularities for each other, and make the total effect more perfect and uniform. 
Mr. Halsted’s automatic incubator is shown in Fig. 31. B is the boiler, heated by a lamp in 
Fig. 3°- 
the usual manner, oil for the lamp being supplied from the reservoir O. D is the egg-drawer or 
nest, above which is the square tank which supplies the heat, a space of two inches being left 
between the tank and top of the drawer to allow room for the regulator. The boiler, B, is 
connected with the heating-tank by the supply and return pipes F and R. The tank was 
identical with the preceding. 
Figs. 32 and 33 show the construction and connections of the boiler and heating-tank, 
which are usually followed still in the best machines of modern make. The conical flue S 
passes through the middle of the boiler, and completes the chimney, opening into the 
atmosphere. The space between -this flue and the outer case of the boiler is divided by a 
cylindrical partition or diaphragm, which reaches from the top to nearly the bottom ; the 
supply pipe F being conducted from the inner and the return pipe R to the outer portion 
of the boiler. The effect of this is to keep up a constant and rapid circulation of the water 
in the direction of the arrows (Fig. 32). The water from the tank passes first into the outer 
portion E, thence under the partition into the inner portion I, where it is rapidly heated, and 
passes off again by the tube F into the tank T (Fig. 33). The boiler is also furnished with 
a stop-cock to draw off the water when required. 
In Mr. Halsted’s machine the supply pipe F was made to branch in the tank, delivering 
