Bui. 1136, U. S. Dept. of Agriculture. 
Plate V. 
Self-Contained Thermostat. 
The large bulb at the right is connected through the armored tube to the bellows in 
the head of the valve. The lower part of the bellows is connected to the stem of 
the balanced steam valve, and the pressure in the bellows tends to close this 
valve. A weighted lever, not shown, acting through the slot below the bellows, 
opposes this pressure and keeps the valve open until the desired temperature is 
reached. 
