84 



GENERAL MANAGEMENT OF POULTRY. 



except in turning them. Air enters, as in the preceding 

 machines, through the hole, D, in the bottom of the incubator, 

 having to pass through canvas soaking in the water-troughs, c c, 

 whence it passes, impregnated with moisture, to the drawer, 

 escaping by the ventilating holes E E. The whole is surrounded 

 as usual by packing. N is a thermometer. 



Fig. 20. Hearson's Incubator. 



The regulation is easily understood. The lamp, T, has a 

 vertical flue, v, above it, as well as the heating-flue, L and if 

 this be opened, of course nearly all the heat escapes by prefer- 

 ence vertically, instead of passing through the tank. The flue 

 v is closed by a flap-valve, F, at the end of a lever, G. Near 

 the pivot end of the lever at P is attached a stiff lifting-wire, 

 which passes through a tube, o, in the centre of the tank ; and 

 the bottom of this wire rests on the capsule, which is simply 

 laid on a small rigid table at s. As the capsule bulges, 



