1018 



POULTRY. 



The ingenious part is the " thermostatic" bar Q. It is a rule in 

 thermostatics that if two pieces of metal be riveted together, one of 

 which expands with heat more than the other, when both are heated 

 the more expansive metal will curve or curl the other in order to find 



Pig. 1873. — Regulator of Tomlinson's Incubator. 



room for its greater expansion. When heated, therefore, the lever Q 

 bends downward, and pulls D down and raises the valve A, and the 

 superheated air escapes. 



Hearson's Regulator.- 



Mr. Hearson, in inventing the Regulator which is shown in Fig. 

 18T4, has made a valuable contribution to the interest of egg incu- 



Piq. 1374.— Incubator Showing Hearson's Regulator. 



bation. The illustration shows an incubator with the Hearson Reg- 

 ulator attached. The action of this Regulator depends for efficiency 

 upon the fixed boiling-pdint of a fluid. A, A is the tanjs of water, 



