CONTROL, OF IXCUBATIKG TEMPERATURES IX L.VBORATORIES. 



9 



temperature in the room, the relay closes the heatin<r-coil circuit. 

 The overload device, 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 operate. 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 breaking the circuit through the overload coil in the main line, 

 thiH cuttino- off the electric cnriont in the entii-e system. 



