206 POULTRY BREEDING 
on incubation, so they may use the incubators they have 
intelligently or to familiarize themselves with the art suf- 
ficiently to make a wise selection of an incubator when 
the purchase of equipment is under consideration. Arti- 
ficial incubation is old as an art but new as a science: 
briefly stated, all that is required to hatch eggs artificially 
is a temperature of 100 2/5° at the center of the egg (101 
to 103° by contact). At the same time the eggs should 
be immersed in still air (quiescent atmosphere) contain- 
ing moisture of relative humidity from +5 to 70 per cent. 
This atmosphere should change sufficiently often to carry 
off the waste gases eliminated by the eggs. Any excess 
of ventilation beyond this may be deleterious. This is 
all that is known about artificial incubation at the present 
time, apart from many things that are known that will 
not work and have a bad effect on the development of the 
eggs. 
“\Vhile the law of incubation seems comparatively sim- 
ple, yet the proper application of these principles in an 
incubator is extremely difficult. They require the use of 
a well-built case to withstand both moisture and changes 
of outside temperature, a reliable and constant source of 
heat, a uniform distribution of the heat so each egg gets 
a uniform quantity, a sensitive and reliable regulation, 
constant ventilation, the constant supply of humidity to 
prevent excessive evaporation of the eggs, all so arranged 
as not to introduce undesirable conditions to work injury 
to the developing embrvo. 
“The best method of obtaining the temperature of the 
center of the egg is with Dr. Wagner's Inovo thermom- 
eter. Eggs are run at a temperature of 100 2/5° the 
entire time of the hatch. To obtain the same degree of 
heat by contact means 102° in cold weather, 101° in 
