Nitw York AGRICULTURAL EXPERIMENT STATION. 197 
dampers, and these dampers are operated by means of com- 
pressed air tubes controlled by metallic thermostats. There is 
also a ventilating flue in the ceiling of each room. The 
thermostat is fixed so as to register some definite temperature 
in each room. For example, in one room the thermostat is sct 
at 70° F. When the temperature falls one degree below 70° F’.., 
the thermostat is affected in such a manner that a valve is 
turned and this causes compressed air to close the cold-air 
damper in the ceiling and to open the hot-air damper in the 
floor, thus restoring the temperature to 70° F. On the other 
hand, when the temperature rises to 71° F., the cold-air flue in 
the ceiling is opened and the hot-air flue is closed, when the 
temperature soon begins to drop. Thus we have an alternate 
admission and exclusion of hot air and cold air, causing the 
temperature to rise a little above or fall slightly below the 
given point at which it is desired to hold the temperature of 
the room. So delicate is the operation of this system that 
merely breathing upon the thermostat will open the cold-air flue, 
while fanning the thermostat will open the hot-air damper. We 
are able, therefore, by this system to hold temperature within 
a very limited range. Under most favorable conditions, the 
limit of variation is only two degrees. Even with a much wider 
temporary variation the temperature of the interior of a cheese 
would not be affected to the extent of more than a small fraction 
of a degree, as we have shown by placing a thermometer inside 
a cheese and keeping it there under observation for several 
weeks. 
CONTROL OF MOISTURB, 
It is more difficult to control moisture than temperature, so 
as to hold it within narrow limits. The most practicable and 
efficient method we have found adapted to our conditions is to 
make use of yard-wide pieces of coarse felt, having a strong 
capillary power. One end of the felt dips in a trough of water 
situated near the top of the room and the lower end drops into 
a trough placed on the floor. The water is sucked in by the 
felt at the upper end and gradually distributes itself throughout 
