CONTROL OF INCUBATING TEMPERATURES IN LABORATORIES. H 
is maintained only a few degrees above that of the surround ing air, 
only small-capacity resistance units are required. 
The special thermostat used in the incubator room is shown in 
figure 8. It is capable of making and breaking the electric circuit 
on a variation in temperature of about 1/100 of a degree F. Tem- 
perature adjustments are made by transferring mercury from the 
small reservoir to the capillary tube, and vice versa. 
A general view of 
the temperature- 
control boards made 
up of commercial 
apparatus is shown 
£-LSCTf7/c coiv/wercr/of/ 
in fisaire 
and 
diagram of the elec- 
tric connections in 
figure 10. Six rooms 
are equipped with 
this apparatus. Re- 
ferring to the dia- 
gram (figure 10), 
one side of the line is 
connected directly to 
the heating coil and 
from the heating coil 
to the line-magnet 
coil. The current in 
this coil is controlled 
by the pilot coil, 
which in turn is con- 
trolled by the ther- 
mostat. When the 
pilot circuit is closed 
through the thermo- 
stat the pilot coil is 
energized and closes 
the circuit throupfh 
the line coil, which acts to close the line circuit through the heating 
coils. When the temperature in the incubation room rises to the 
upper limit the thermostat makes contact with the stop point, thus 
breaking the pilot circuit and opening the line coil, and hence the 
current in the heating coils. 
TEMPERATURE RECORDERS. 
Each incubation room is fitted with a continuous T-day recording 
thermometer. The recording elements are mounted on the wall out- 
side the room and the capillary passes through the wall, the bulb 
Fig. 8. 
-Mercury thermostat used in temperature-control 
system of Pathological Division. 
