The wall thermometers are designed for the purpose of taking the
temperature of the copper wall rather than the temperature of the air.
When temperature fluctuations are being experienced inside of the
respiration chamber, the air obviously shows temperature fluctuations
first, and the copper walls are next affected. Since in making
corrections for the hydrothermal equivalent of the apparatus and for
changes in the temperature of the apparatus as a whole it is desirable
to know the temperature changes of the wall rather than the air, these
wall thermometers were installed for this special purpose. In
construction they are not unlike the thermometers used in the air, but
instead of being surrounded by perforated metal they are encased in
copper boxes soldered directly to the wall. Five such thermometers are
used in series and, though attached permanently to the wall, they are
placed in relatively the same position as the air thermometers. The two
terminals are conducted through the metal walls to the observer's table,
where variations in resistance are measured. The resistance of the five
thermometers is not far from 20 ohms.