Artificial Incubation. 
35 
machines require very little heat, so that a very small lamp will suffice ; for large ones requiring more heat 
the Bismarck 3 and 4-inch circular burners are most satisfactory, and perfectly safe. The top of the chimney 
should be about half an inch from the bottom of the boiler. The best thermometer is a round glass one, 
about a foot long, procurable at a cost of three or four shillings, accurately tested. This rests on the eggs, 
and is inserted through a hole in the front of the drawer ; a piece of ribbon attached to it permits it to be 
withdrawn at any time. 
Fig. 27 shows the plan of the top of the machine, and position of inlet, outlet, damper, and regulator rods. 
Fig. 28 shows a cross section through the centre of the machine, with the regulator in position ; D is 
the thumb-screw for adjusting the damper, E, which is made of thin metal and circular, rather larger in 
diameter than the reguiator-fiue, F. This flue, when opened by the regulator carries off any excess heat from 
Fig. 27.— Plan of Top of Machine, 
the egg-drawer itself, therefore that portion of the machine can never get beyond the required temperature. 
A is the adjusting-screw of the regulator, and by means of which the machine may be set to a fraction of a 
degree of any desired heat. G G shows the boiler, with the circulating diaphragm. C and / are the 
bearings of the regulator. K is the capsule, which on expanding, forces up the short end of the lower rod, 
and thereby depresses the long end, and in turn, pulling on the bearing, C, causes the damper, E, to rise 
sufficiently to allow the surplus heat to escape, when the damper, £, will again close the flue, F. L is an 
iron bar one inch wide by a quarter thick, extending from front to back of the machine, and on which the 
bearing, J, is screwed, and the capsule, K, rests. A plate of metal about i8-gauge should be placed on the 
rod, under the capsule, to prevent the latter from buckling. It will be noticed that the tank is domed from 
front to back, and that the bottom of the egg-drawer is correspondingly dished ; this is to ensure that any egg 
Fig. 28.— Cross Section, centre of the Machine, 
gets an equal amount of heat to any other, no matter in what part of the drawer. In small machines, say 
under 30 eggs, the bottom of the tank may be flat, the drawer only dished, but in the larger machines the 
doming and dishing increase with the size. There is a packing of sawdust well rammed on top, sides, and 
ends of tank ; the casing up to level of bottom of tank is made double, also the front of drawer. For the 
bottom of the egg-drawer use half-inch mesh wire netting, and press into the shape required ; spread a piece 
of porous flannel over the netting, for the eggs to lie on. 
Fig. 29 shows the bottom of the machine, with holes bored for ventilation. These may be of half-inch 
size ; the centre group of large ones, say one-inch, should be provided with a sliding cover, as they are only 
required occasionally, as will be pointed out later on. 
