82 GENERAL MANAGEMENT OF POULTRY. 



Messrs. Christy and Co. have since 1883 brought out their 

 patent " therinostatic " incubator, which also works by the 

 constant heat of a small lamp under a circulating boiler 

 outside the machine. It is shown in section in Fig. 1 9. The 

 hot water tank, with the horizontal partition, is shown at u, 

 and is fed by pipes R and R', from the small conical boiler 

 H over the lamp s. The tank-bottom is sloped so as 

 to give a slight dome-shape to the top of the air or egg- 

 chamber, and from this ascends the air-shaft B capped by the 

 regulator-valve A. All the air enters from the bottom by the 

 apertures L L, as in Mr. Tomlinson's machine, in doing which 

 it has to pass through canvas, T, which dips all round into 

 evaporating pans or troughs of water, and is kept constantly 

 moist. Thence it passes through perforated zinc to the eggs- 

 In this way the air is kept in free circulation, stagnation in 

 the centre of the door being quite prevented, and it is un- 

 necessary to change the places of the eggs, or do more than 

 turn and cool them. 



The regulator Q is a thermostatic bar, similar in principle 

 to the balance of a " compensated " watch. If two strips of 

 different metal are riveted together, one of which expands 

 with heat more than the other, the one which expands 

 most must curl the other more or less, that it may find 

 room for its expansion at the circumference of a larger or 

 outer circle. With heat, therefore, the free end of the bar Q 

 curls downwards somewhat, and thus pulls down the end, D, 

 of a lever which raises the valve, A, and lets out warm air. 

 c is an adjusting screw to set the valve, and F merely 

 a wire-cage to protect the regulator from injury. N is the 

 thermometer, o the lamp reservoir, and p a sliding shelf, which 

 pushes up the lamp towards the boiler and chimney. 



In these machines the lamps should be trimmed every 

 twelve hours, always turning the eggs first, before this is done, 

 to keep them from the smell as much as possible. The open 



