320 



CENTRAL SCIENTIFIC CO., CHICAGO, U. S. A. 



No. 7908. 

 Size No. 41. 



No. 7908. 

 Size No. 1. 



No. 7908. 

 Size No. 33. 



Electro-Thermostat of No. 7908. 



INCUBATORS, Electric, Wood Frame, with electro-thermostatie control. 



Construction: The walls are constructed of successive layers of transite, tar paper, animal hair, 

 tar paper and five-ply wood, the latter consisting of quarter sawed oak over fibrous chestnut. 

 The No. 1 Incubator, because of its small size, is sheathed with a solid wall of quarter- 

 sawed oak % inch in thickness. The others all have the five-ply construction. By this con- 

 struction, excellent insulation is secured, without danger of warping under the influence of 

 heat or capillary moisture from inside the incubating chamber. The doors are provided with 

 glass for observation of the contents, except in the larger sizes (Nos. 11-41), where an inner 

 door of glass is provided with the entire outer door made of wood. The outer wall of quarter- 

 sawed oak is finished in the natural color and highly polished. 



Heating is accomplished by means of incandescent carbon filament lamps, which heat quickly 

 and cool quickly. The sizes of these are selected according to the cubic contents to be 

 heated. If specified when ordered, the incubators can be furnished with wire wound electric 

 heaters with pilot lights. 



Ventilation is provided for by means of two holes in the smaller sizes, one near the bottom 

 through which cold air enters, the other at the top through which the warm air escapes. In 

 the larger sizes, there are four holes for entrance and escape of air, and the lamps are pro- 

 vided with chimneys for the purpose of creating air currents. In this manner, a constant air 

 current is maintained. 



Regulation of the temperature is effected by means of the electro-thermostat, which consists of a 

 diaphragm of hard rubber and a metal disk riveted together. The difference in the expansion 

 of the hard rubber and metal causes the former to become cup-shaped thus moving forward 

 the center to which a platinum contact is attached. As the temperature is lowered the motion 

 is reversed. By this means contact is alternately made and broken between two platinum 

 points in circuit with the lamps, one attached to the diaphragm, the other to a thumb screw 

 passing through the bridge across the thermostat, thus controlling the temperature. A con- 

 denser is provided by which the electric spark between the contact points is quenched, pre- 

 venting the points from being quickly used up. The thermostat and condenser are mounted 

 on a transite base. 



