1911] LAND—CONSTANT TEMPERATURE APPARATUS 399 
to his interest in the problem and his skill in construction that the 
apparatus has proved so efficient in this laboratory. He has 
recently devised a form of this thermostat which can be used 
with safety where explosive gases are present. He finds that when 
made as described here the cost should not exceed $15.00 for the 
apparatus complete and ready to attach to the incubator. 
THE UNIVERSITY oF CHICAGO 
