INCUBATING OVENS AND THERMO-REGULATORS. 9& 



of this simple and convenient incubating oven are manufactured by 

 Rohrbeck and by Miincke, of Berlin. The apparatus of D'Arson- 

 val, and other forms in favor at the French capital, may be obtained 

 from Wiesnegg, of Paris. The last-named manufacturer also sup- 

 plies the incubating oven and thermo-regulator recently described by 

 Roux (1891). This is shown in Fig. G9. The regulator is formed of 

 two metallic bars, one of steel and the other of zinc ; these are 

 soldered together in the shape of a letter U ; the regulator is seen in 

 position in the cut (Fig. 69). The most dilatable metal (zinc) is on 

 the outside. When the temperature is raised the arms of the U ap- 

 proach each other, and the reverse when it falls. The method by 

 which regulation is effected is shown in Fig. 70. The U-shaped 

 regulator is placed vertically, and one of its branches, A, is firmly 

 fixed to the wall of the incubating oven ; the other, free arm car- 

 ries a horizontal bar which projects through the wall of the incu- 

 bator in an opening which permits it to move freely under the influ- 

 ence of a change in the temperature within. The end of this 

 projecting bar is turned up at a right angle and the screw p passes 

 through it ; this can be fixed at any desired point by means of the 

 nut e. The end of the screw p rests against the stem of a conical 

 brass valve which controls the flow of gas. The valve is closed by a 

 spiral spring and opened by the screw p under the control of the 

 thermo-regulator. 



