rections therefor. The influence of such pressure upon thermometers
used in an apparatus of this type was first pointed out by Armsby,[8]
and with high rates of flow, amounting to 1 liter or more per minute,
there may be a correction on these thermometers amounting to several
hundredths of a degree. We have found that, as installed at present,
with a rate of flow of less than 400 cubic centimeters per minute, there
is no correction for water pressure.

In installing a thermometer it is of the greatest importance that there
be no pressure against the side of the tube through which the
thermometer is inserted. The slightest pressure will cause considerable
rise in the mercury column. Special precautions must also be taken to
insulate the tube through which the water passes, as the passage of the
water along the tube does not insure ordinarily a thorough mixing, and
by moving the thermometer bulb from the center of the tube to a point
near the edge, the water, which at the edge may be somewhat warmer than
at the center, immediately affects the thermometer. By use of the vacuum
jacket mentioned above, this warming of the water has been avoided, and
in electric-resistance thermometers special precautions are taken not
only with regard to the relative position of the bulb of the mercury
thermometer and the resistance thermometer, but also with regard to the
hard-rubber insulation, to avoid errors of this nature.

ELECTRIC-RESISTANCE THERMOMETERS.

Electric-resistance thermometers are used in connection with the
respiration calorimeter for several purposes: first, to determine the
fluctuations in the temperature of the air inside the chamber; second,
to measure the fluctuations of the temperature of the copper wall of the
respiration chamber; third, for determining the variations in body
temperature; finally, for recording the differences in temperature of
the incoming and outgoing water. While these thermometers are all built
on the same principle, their installation is very different, and a word
regarding the method of using each is necessary.

AIR THERMOMETERS.

The air thermometers are designed with a special view to taking quickly
the temperature of the air. Five thermometers, each having a resistance
of not far from 4 ohms, are connected in series and suspended 3.5
centimeters from the wall on hooks inside the chamber. They are
surrounded for protection, first, with a perforated metal cylinder, and
outside this