Artificial Incubation. 
29 
more even expansion is ensured than would otherwise be the case. The expansion of this hciuid in the 
margin of ten degrees immediately above and below its boiling point is seven times greater than that of any 
known metal,. and it exerts a corresponding amount of force in tlie work which it has to perform. The 
bracket in which it is placed is suspended by bolts from the floor of the drying box, where the pivot of the 
level arm which connects with the lamp is also fastened, so that any warping or expansion, however slight, 
cannot lengthen or shorten the distance between the capsule and the level arm by even the veriest fraction of 
an inch, though a minute shift at this point, which is often caused by the greater or lesser pressure of the water 
in the tank, will upset at times the action of the regulator in a most unaccountable manner. The bracket is 
immediately over the egg-drawer, and a block of wood placed between the capsule and the»tank intercepts the 
rays of heat from the tank, so that only the heat of the eggs themselves can affect the capsule — a most 
important provision. The level arm connects with a most simple slide, which rises over the wick of the 
lamp when the regulator is acting, actually ensuring that the flame is the proper height for keeping the 
Incubator at the correct temperature. The effectiveness of this method of regulation is proved by tlie 
number of Incubators introduced since first the Excelsior was brought out, in which the regulator is more or 
less of this pattern. The regulator is controlled and adjusted by means of a screw, on the end of the level ann 
outside the Inaihatov, which shortens or lengthens the connection between the lamp slide and the level arm, 
upon which is a sliding weight, which is placed along towards the lamp, and not removed after adjustment 
by the screws and end of the lever arm. This method of regulation in the Excelsior greatly economises the 
amount of oil used in heating the water. The arrangement of the tank around the egg-chamber forms a 
circuit, and the water being heated at one side of the circuit rises, while the colder water from the tubes 
takes its place, causing the whole body of water to circulate round the egg drawer, and travel to and from the 
lamp. Thus the whole heat of the lamp is absorbed direct by the water without any waste through inter- 
mediate flues. 
Until comparatively quite recently it has been a generally accepted theory in Incubator manufacture 
that to ensure an even temperature in the egg-chamber, the body of water from which the heat is radiated 
must be large. If the egg-chamber were an isolated space, this would, of course, be correct ; but as it is 
absolutely necessary that it must be well ventilated, the theory referred to must, on close consideration, be 
found erroneous. Assuming that with the ventilating air entering the egg-chamber at 45 deg. Fahr., a heat 
of 130 deg. Fahr. would be necessary in the tank to keep the egg-chamber at 10 1 deg. Fahr. Then if the 
outside air increases in heat twenty degrees or more, there will be a considerable increase in the interior 
temperature also, unless the temperature of the tank falls, which it will not readily do if the body of water 
is of large dimensions. In other words, to ensure the regularity of heat in the egg-chamber the temperature 
of the water must imperatively vary in inverse proportion to the temperature of the room in which the 
machine is working. This principle was first recognised in the Excelsior, the tank of which contains a small 
body of water compared to the extent of its radiating surface, allowing it to change its temperature 
QUICKLY, in response to the action of the regulator upon the lamp. It has often been observed 
with many Incubators, even with the action of their regulators, that it is compulsory to 
extinguish the lamp on hot days, and frequently then the temperature will remain too high. Even in the 
warmest parts of Australia the heat in the shade rarely reaches 10 1 deg. Fahr. during the hatching season, and 
it is, therefore, a complete anomaly for the heat of the egg-chamber to rise more than a degree or two above 
this. The sequel is found in the fact that the tank in many machines does not cool quickly on hot days, 
and, being hotter than the proper temperature for the eggs, accounts for the increasing heat, even when the 
lamp is extinguished. With the " E.xcelsior" the lamp may be left burning even on the warmest days ; the 
machine answering almost immediately to the regulator, the heat cannot rise. On an exceptionally hot day 
the tank of a 200-egg machine often registers 102 deg. Fahr. with the lamp still burning, the eggs being 
loi or loij^ deg. Fahr. Provision for the chicks when first hatched is provided by a roomy drying-box 
occupying the whole top surface of the machine. The level arm connecting the pin rising from the capsule 
with the chain leading to the lamp is fixed inside of the drying-box, in order that the top of the Incubator 
will be table-like. The chicks are prevented from touching the level arm by a guard placed around it. 
