
CONTROL OF INCUBATING TEMPERATURES IN LABORATORIES. 
9 
temperature in the room, the rela}^ closes the heating-coil circuit. 
The overload cleAdce, shown in the diagram, has for its object the cut- 
ting out of the whole system in case the temperature-control appa- 
ratus fails to oj^erate. In principle it is identical with the tempera- 
ture-control equipment. The overload thermostat is adjusted to close 
the electric circuit through the overload relay at a room temperature 
a few degrees above the normal operating temperature, the relay in 
turn brealdng the circuit through the overload coil in the main line, 
thus cutting oif the electric current in the entire system. 
