Artificial Incubation. 
27 
machines if connected up in multiple. It is advisable to use magnets of not less than fifty ohms resistance, 
as they are more powerful, and will permit you to use four cells. Should you use magnets of four weight 
ohms resistance, they would not operate on four cells at all, as the vitriol resistance of four gravity cells is 
greater than that. 
Ventilation. 
The egg absorbs oxygen and exhales carbonic acid gas. This gas is heavier than air, and, as a result, 
will settle at the bottom of the egg-chamber. Should the escape of this gas be prevented by faulty ventila- 
tion, the embryo chicken will die of cyanosis, or lack of oxygen. This simple fact commends to us the 
proper plan of ventilation — viz., holes in the bottom of the egg-chamber for the escape of the carbonic acid 
gas, and an opening in the top for fresh air. The carbonic acid gas and cold air which escape through the 
holes in tJie bottom of the air chamber will produce a suction strong enough to prevent the warm air from 
escaping through the top hole. Fig. 21. If the air vent is arranged as per illustration it will be properly 
heated by passing alongside the lamp flue. There will be so much warm air in motion and entering this tube 
that it will be practically impossible for any of the air in the chamber to escape. 
Fig. 21. 
Moisture. 
The directions accompanying most machines call for too much moisture." I am fairly convinced that 
very little moisture is necessary, and then only at the end of the hatch, about the eighteenth da.y. There are 
some, however, who go to the extreme of not giving enough moisture, or none at all. Possibly the best 
plan to pursue is to notice the size of the air space of the egg. If the air space on the eighth or ninth day 
indicates much evaporation, place a pan of water in the egg-chamber, and permit it to remain there 24 
hours, and then- remove it. Repeat this as often as necessary until the eighteenth day, and after that keep 
water in the egg-chamber until the eggs are all hatched. This observation of the air space in the egg requires 
great care and judgment. There are no rules to be laid down, experience is the only teacher in this case. 
The following descriptions of some of the best Incubators now on the market will, no doubt, be read 
with interest : — The Johnston's Excelsior and A.B.C. Incubators are manufactured by Mr. R. Johnston, of 
Chappelow Estate, Hurstville, N.S.W. : The drawer of the Excelsior differs from that of the majority 
of Incubators, in that the bottom of the egg-drawer is perfectly level, and this is done without 
sacrificing the advantages of the hollow drawer, i.e., a uniform heat in all parts ; in fact, the 
protection of the outer parts of the drawer is perfect. The tank extends over the top of the egg-chamber 
and down on each side, connecting the two sides. Underneath the drawer, and at the lowest level, are two 
broad flat tubes, one at the front and the other at the back of the machine. A projection from the tank at 
its lowest point extends over the lamp. Thus the sides of the egg-drawer are protected by the sides of the 
