JOHN H. NORTHROP 311 



runs off from the top of the water gauge on the side of the incubator 

 (not shown in Fig. 1). 



The adjustment for temperatures below room temperature is 

 identical except that cold water is run through A and the relay so 

 adjusted that the water runs into the incubator when the circuit is 

 closed and to waste when the circuit is open. Temperatures to 8 or 

 10°C. may easily be maintained by the use of ice water. 



When temperatures within the range of variation of the room are 

 desired, a slow, continuous stream of cold water is run through the 

 incubator and warm water is run through the pipette connected with 

 the regulating device. 



