INCUBATING OVENS AND THERMO-REGULATORS. 93 



Another platinum wire passes down the tube of the thermometer, b, 

 and is adjustable for any desired temperature. The gas passes 

 through a valve which is controlled by an electro-magnet. A 

 simple form of valve is shown in Fig. G7. The bent tube a is con- 

 nected with the gas supply by a piece of rubber tubing. The up- 

 right arm of this tube is enclosed in a larger tube, b, having an out- 





FIG. 68. FIG. 69. 



let, e, which is connected with the burner under the incubating 

 oven. The upper end of this larger tube is closed by means of a 

 piece of sheet rubber, which prevents the escape of gas. When this 

 is depressed by means of the lever c, the flow of gas through the 

 valve is arrested. The lever c has attached to it the armature d, 

 and is operated by an electro-magnet under the control of the regu- 

 lating thermometer. 



