POUL TR Y-CRAFT. 177 
Don't try to force the temperature up, as it will incline to raise rather than lower, unless 
the room in which you have the machine is very cold; but on the contrary, if the 
machine goes up to 103 degrees, and is going over that point, you will have to adjust the 
regulator @ éit¢/le.”  (McFetridge). 
256. Ventilation and Moisture.— The egg chamber requires to be 
ventilated, that the gases generated in the eggs may be promptly thrown off. 
The currents of air created by ventilation may cause a more rapid evaporation 
of the fluids of the egg than takes place in natural incubation. Some 
operators use no moisture, some none until the seventeenth or eighteenth day, 
some @ /é¢t/e throughout the hatch. The principle upon which the 
application of moisture depends is thus lucidly explained by Cyphers : 
‘‘Evaporation from the egg must be held at such a point that the fluids in the 
embryonic structures are ample to keep the membranes moist up to the time of exclusion, 
and the rate of evaporation is not the same under any two degrees of temperature. Eggs 
may be successfully incubated under a temperature that will exclude the chick by the 
beginning of the nineteenth day, or under one that will not exclude the chick until the 
twenty-second. The most vigorous chicks will be produced when the eggs are incubated 
under a temperature that will ripen the embryo by the close of the twentieth day; and any 
variation from this temperature will proportionately affect the vitality of the chicks and 
lower the percentage of the hatch. If we have a rate of evaporation to balance the 
temperature for a twenty-day exclusion, this rate of evaporation will not answer for a 
nineteen or a twenty-one-day —there being too great an amount of evaporation for a 
nineteen-day, and too little for a twenty-one-day. In neither case will many of the eggs 
hatch, but if we supply more humidity (the rate of movement of the air remaining the 
same) for a nineteen-day, and less for a twenty-one-day exclusion, we will have a chance 
for a fair hatch. If we have a degree of humidity to balance a twenty-day exclusion, and 
then raise or lower the temperature half a degree, it will injuriously affect the hatch, 
while a greater variation will ruin it. A constant variation of a degree in temperature 
will have no injurious effect, but if the temperature is permanently raised or lowered a 
degree, the atmospheric conditions for a twenty-day exclusion will not answer. 
“Tt has been universally believed that evaporation from the eggs could only be con- 
trolled by controlling the humidity of the air in the hatching chamber. The humidity of 
the air is but one controlling factor, however, as with the same degree of humidity 
evaporation will be slow or rapid according to the rate of movement of the air, while it 
is not the same under any two degrees of temperature; and the constant variation in these 
two factors is the cause of the extremely varying results. With a due appreciation of 
these facts, artificial incubation should be more successfully prosecuted in the future than 
it has been in the past. 
‘‘Evaporation is mainly influenced by the rate of movement of the air within the: 
hatching chamber, and secondarily by the degree of humidity. The rate of movement of 
the air is controlled by the area and location of the ventilating openings and temperature 
of the outer atmosphere. The degree of humidity cannot be maintained constant when 
maintaining a constant movement of the air, and it is not necessary that it should be. 
The first consideration is to secure a constant rate of movement, and then keep the air 
from becoming too dry. This is practically all that is necessary in supplying humidity 
when the rate of movement of the air is maintained constant.” 
Cyphers’ rules for ventilating, applying specially to bottom ventilation, will 
not be given here. His method is to adjust the ventilation to keep the air 
