e 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.

ELECTRICAL RECTAL THERMOMETER.

The resistance thermometer used for measuring the temperature of the
body of the man is of a somewhat different type, since it is necessary
to wind the coil in a compact form, inclose it in a pure silver tube,
and connect it with suitable rubber-covered connections, so that it can
be inserted deep in the rectum. The apparatus has been described in a
number of publications.[9] The resistance of this system is also not far
from 20 ohms, thus simplifying the use of the apparatus already
installed on the observer's table.

ELECTRIC-RESISTANCE THERMOMETERS FOR THE WATER-CURRENT.

The measurement of the temperature differences of the water-current by
the electric-resistance thermometer was tried a number of years ago by
Rosa,[10] but the results were not invariably satisfactory and in all
the subsequent experimenting the resistance thermometer could not be
used with satisfaction. More recently, plans were made to incorporate
some of the results of the rapidly accumulating experience in the use of
resistance thermometers and consequently an electric-resistance
thermometer was devised to meet the conditions of experimentation with
the respiration calorimeter by Dr. E. F. Northrup, of the Leeds &
Northrup Company, of Philadelphia. The conditions to be met were that
the thermometers should take rapidly the temperature of the ingoing and
outcoming water and that the fluctuations in temperature difference as
measured by the resistance thermometers should be controlled for
calibration purposes by the differences in temperature of the mercurial
thermometers.

[Illustration: FIG. 16.--Details of resistance thermometers for
water-circuit. Upper part of figure shows a sketch of the outside of the
hard-rubber case. In lower part is a section showing interior
construction. Flattened lead tube wound about central brass tube
contains the resistance wire. A is enlarged part of the case forming a
chamber for the mercury bulb. Arrows indicate direction of flow on
resistance thermometer for ingoing water.]

For the resistance thermometer, Dr. Northrup has used, instead of
copper, pure nickel wire, which has a much higher resistance and thus
enables a much greater total resistance to be inclosed in a given space.
Th