28 
The Australasian Book of Poultry. 
tank, and the front and back by the tubes immediately underneath. But the advantage of a level egg- 
drawer, while still retaining a uniform temperature in all i)arts, though making the process of filling with and 
turning the eggs much easier, is small compared to the evenness of temperature secured by heating the 
current of ventilating air. The apertures for the ingress of air are immediately beneath the tubes referred to, 
against which the air rushes, and afterwards passes to the centre of the machine, rising through the holes 
provided in the moisture pan, which is placed under the drawer, between the tubes entering the egg-drawer 
through tile perforated zinc iiottom, and making its exit through the rows of holes at the front and back of 
the machine. The effect of this is seen in the temperature to be maintained. The correct average heat of 
the whole of the eggs during incubation is loi deg Fahr. In any Incubator in which the heat is solely 
radiated from the top to the eggs, and in which the thermometer rests at an equal level with the top of the 
eggs, it must, to give good results, register from 102 to 104 deg. Fahr., the latter heat being necessary in the 
coldest weather, the former being sufficient in warm. Ikit the average heat is still, or should be, 'loi deg. 
Fahr. 'I'he reason for this variation is that in cold weather the difference between the top and bottom of the 
egg is much greater tlian in warm, because the ventilating air enters at a lower temperature. This apparent 
anomaly of different temperature is avoided in the Excelsior, the whole of each egg being kept at a uniform 
average. temperature of loi deg. Fahr. In arriving at the proper heat for artificial incubation it seems 
somewhat strange to say that the final decision as to what is correct is not taken from any observation of the 
hen while sitting, but from actual results obtained with the Incubator. Tests of the heat of the side of the 
eggs nearest the hen's body have been^obtained as high as 106 deg. Fahr. ; but few, indeed, would advocate 
this as the correct temperature for eggs in an Incubator. It is generally known that perfectly fresh fertile 
eggs will hatch a day or two earlier than the recognised time if the heat of the Incubator is maintained a 
degree or two higher than the proper average temperature, i.e., 103 deg. Fahr. ; while, on the other hand, a 
slight lowering of the temperature below the latter will retard the hatching. Here, then, is a definite data 
upon which to proceed. Ordinarily, fresh fertile eggs should be all hatched out in twenty days twelve hours, 
or thereabouts. 
The capsule used in the Excelsior contains a fluid which, when open to the atmosphere, boils at 
ioo'5 deg. Fahr. ; but with the pressure exercised upon it by the various connections it boils at about i deg. 
higher, so that its greatest expansion is at half a degree above that of the normal temperature of the egg. 
The fluid being a definite chemical compound, and not a mere mechanical mixture or solution, a better and 
