Oct. 27, 1923 
Automatic Control of Low Temperature 
187 
tained in the culture room during this time. The lower chart of the group 
shows the temperature maintained in the coil room during the same 
period. Check readings of the temperature in the culture room were also 
taken from time to time by means of a high-grade mercurial thermometer. 
Attention is called to the fact that the middle chart shows the tempera¬ 
ture of the air in the culture room, but since the cultures were propa- 
Fks. 3.— Typical temperature charts from indoor compartments. The apparent gradual rise of tempera¬ 
ture in culture room is due to the blank form having been slightly inclined when placed around the 
cylinder. 
gated in water, the variations in temperature of the water were much 
less than those of the air in the room. 
The temperature of the outside air varied between 52 and 90° F., 
while the temperature of the liquid in which the plants were propagated 
varied between the limits of ±0.18° F. (o.i° C.). 
This portion of the plant was originally designed for maintaining a 
practically constant temperature at or about 18° C. (± 64.4° F.). Experi¬ 
ments have been conducted, however, at different temperatures between 
18° C. and the freezing point, and the equipment has given satisfactory 
results at any adjustment between these points. Closer control could 
have been obtained at the lower temperature had the plant been designed 
for operation at the lower temperature. 
