342 ARTIFICIAL INCUBATION 
sirability of retarding evaporation in artificial incubation by in- 
creasing the humidity of the air in the egg chamber, yet at the same 
time permitting free ventilation. 
Experiments have been conducted involving one thousand 
eggs set in eight machines, four with low and four with high 
humidity, the average in the dry machines being 56 degrees, and 
in the wet 68 degrees. The results showed that increased moisture 
was desirable, and that there was much less loss in weight during 
the incubating period. The average loss of weight for the wet 
machines was 0.145 pound, and for the dry 0.23 pound, being nearly 
double in the case of the dry machines. 
This same experiment also proved that increasing the moisture 
within certain limits produced the following results: (1) It in- 
creased the percentage of hatch, which was 62.0 per cent for the 
dry and 69.6 per cent for the wet. (2) The resulting chicks 
weighed much more at hatching time and were more vigorous, being 
0.079 for the dry and 0.081 for the wet, there being five cripples 
in the dry machines against one in the wet. (3) Produced greater 
uniformity in the hatch, both from the standpoint of lapse of 
time from pipping to complete hatching, as well as uniformity in 
the chicks themselves. (4) The chicks from the moisture machines 
were much more successfully brooded, the percentage being 52.3 
for the dry against 89.5 for the wet. 
The retardation of evaporation is an important matter. The 
extent to which it should be carried depends on atmospheric con- 
ditions surrounding the egg and in the incubator room. Evapora- 
tion may be checked by increasing the humidity in any of the 
following ways: By frequent sprinkling of the floor and walls with 
water; by placing under the egg trays moisture pans, usually filled 
with sand which is kept wet; by putting a sponge or other material 
saturated with water in the machine; by sprinkling the eggs at 
frequent intervals with warm water; or by limiting the ventilation 
by partially closing the ventilators. 
As a matter of fact, it is doubtful whether the humidity can 
be kept too high. Humidity is ascertained by an instrument 
called a hygrometer. The degree of moisture is computed by 
comparing the readings from two thermometers, the bulb of one 
being wrapped in a moist wick or cloth, while the other is dry. 
The lower reading of the wet bulb is due to evaporation, hence 
the difference between the two readings. The amount of evapora- 
tion depends upon the humidity in the air. It is impossible to 
