THE PEOPLE'S PRACTICAL POULTRY BOOK. 



OF THE \ 



UNIVE&SITY 



degree of temperature in incubators heated by water, and it T^^gU^Qwg*;; 

 of two horizontal glass tubes, closed at one end, containing alcoHQt,' an 

 located under the hot water tank, each tube communicating with a vertical 

 cylinder filled with mercury, one at each end of the incubator; in which 

 cylinders are cork pistons or floats, having rods attached to pivoted levers, 

 which are so connected with the regulators on the heating lamps and ven- 

 tilating valves, communicating with the incubating chamber, that the rising 

 of said floats or pistons beyond a certain point by the expansion of the 

 alcohol will act to check the flames of the lamps and open the ventilating 

 valves, thus decreasing the temperature of the air and water, while the de- 

 pression of said floats, in consequence of the contraction of the alcohol, will 

 produce an opposite effect and highten the temperature, the parts being so 

 arranged as not to be affected by the medium temperature, at which the 

 incubator is to be kept, but only by higher or lower degrees. 



EXPLANATION OF THE ILLUSTRATION. 



In the drawing A represents the incubator, which is divided into several 

 compartments, as shown in figure 2, viz. : The cold water tank, B ; in- 

 cubating space, C ; hot water tank, D ; protecting or heat-retaining space, 

 E ; and drying loft, F. The ends of the incubator are provided with lamps, 

 G, which heat the water in reservoirs, H. These latter communicate, 

 through tubes, I, I, with the hot water tank, D. J, is a reservoir, which 



FIG. S.-TRANSVERSE SECTION OF GRAVES' INCUBATOR. 



supplies oil to the lamps. K, K, represent glass tubes under tank, D, and in 

 contact with the bottom thereof. Said tubes are filled with alcohol, or other 

 expansible fluid, and communicate at their outer ends through the bent 

 tubes, L, with the cylinders, M, which contain mercury. N, represents a 

 piston rod, attached to a cork piston, or float, N, in the cylinder, M. The 



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