INCUBATION 
same station in which the loss for the three periods was 5.63, 
9.18 and 2.15. 
I think the reader is now in position to appreciate the almost 
unsurmountable difficulties in the proper control of evapora- 
tion with the common small incubator in our climate. It is 
little wonder that one of our best incubator manufacturers, 
after studying the proposition for some time, threw over the 
whole moisture proposition, and put out a machine in which 
drafts of air were slowed down by felt diaphragms and the 
use of moisture was strictly forbidden. 
The moisture problem to the small incubator operator pre- 
sents itself as follows: If left to the mercies of chance and 
the weather, the too great or too little evaporation from his 
eggs will yield hatches that will prove unprofitable. In order 
to regulate this evaporation, he must know and be able to 
control both vapor pressure and the currents of air that strike 
the eggs. Now he does not know the amount of vapor pres- 
sure and has no way of finding it out. The so-called humidity 
gauges on the market are practically worthless, and even were 
the readings on relative humidity accurately determined, they 
would be wholly confusing, for their effect of the same relative 
humidity on the evaporation will vary widely with variations 
of the out-of-door temperature. : 
If the operator knows or guesses that the humidity is too 
low, he can increase it by adding water to the room, or the 
egg chamber, but he cannot tell when he has too much, nor 
can he reduce the vapor pressure of the air on rainy days 
when nature gives him too much water. As to air currents 
he is little better off—he has no way to tell accurately as to 
the behavior of air in the egg chamber and changes in tem- 
perature of the heater or if the outside air will throw these 
currents all off, since they depend upon the draft principle. 
Taking it all in all, the man with the small incubator had 
better follow the manufacturer’s directions and trust to luck. 
The writer has long been of the conviction that a plan which 
would keep the rate of evaporation within as narrow bounds 
as we now keep the temperature, would not only solve the 
problem of artificial incubation, but improve on nature and in- 
crease not only the numbers but the vitality or livability of the 
chicks. With a view of studying further the relations between 
the conditions of atmospheric vapor pressure, and the success 
of artificial incubation, I have investigated climatic reports 
and hatching records in the various sections of the world. 
The following are averages of the monthly vapor pressures 
at four points in which we are interested: 
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