e insulated nickel wire is wound in a flattened spiral and then passed
through a thin lead tube flattened somewhat. This lead tube is then
wound around a central core and the flattened portions attached at such
an angle that the water passing through the tubes has a tendency to be
directed away from the center and against the outer wall, thus insuring
a mixing of the water. Space is left for the insertion of the mercurial
thermometer. With the thermometer for the ingoing water, it was found
necessary to extend the bulb somewhat beyond the resistance coil, so
that the water might be thoroughly mixed before reaching the bulb and
thus insure a steady temperature. Thus it was found necessary to enlarge
the chamber A (fig. 16) somewhat and the tube leading out of the
thermometer, so that the bulb of the thermometer itself could be placed
almost directly at the opening of the exit tube. Under these conditions
perfect mixing of water and constancy of temperature were obtained.

In the case of the thermometer which measured the outcoming water, the
difficulty was not so great, as the outcoming water is somewhat nearer
the temperature of the chamber, and the water as it leaves the
thermometer passes first over the mercurial thermometer and then over
the resistance thermometer. By means of a long series of tests it was
found possible to adjust these resistance thermometers so that the
variations in resistance were in direct proportion to the temperature
changes noted on the mercurial thermometers. Obviously, these
differences in resistance of the two thermometers can be measured
directly with the Wheatstone bridge, but, what is more satisfactory,
they are measured and recorded directly on a special type of automatic
recorder described beyond.

OBSERVER'S TABLE.

The measurements of the temperature of the respiration chamber, of the
water-current, and of the body temperature of the man, as well as the
heating and cooling of the air-spaces about the calorimeter, are all
under the control of the physical assistant. The apparatus for these
temperature controls and measurements is all collected compactly on a
table, the so-called "observer's table." At this, the physical assistant
sits throughout the experiments. For convenience in observing the
mercurial thermometers in the water-current and general inspection of
the whole apparatus, this table is placed on an elevated platform, shown
in fig. 3. Directly in front of the table the