METHODS AND APPARATUS. 



27 



cision used. Slight differences will be noted among the several junctions in 

 the calibrations given. These are not due to experimental error, as the 

 figures reproduce themselves very well; the cause is probably to be found in 

 a slight inhomogeneity of the constantan wire at the different junctions. In 

 actual experimenting the potentiometer balance is obtained, and by means 

 of the calibration curves just described the corresponding value of the tem- 

 perature difference can at once be found. 



A SAMPLE BODY-TEMPERATURE EXPERIMENT. 



In an experiment the junctions are placed at the different points where 

 it is desired to obtain the temperature, being held in position when necessary 

 by a strap or bandage. The apparatus is then operated in the manner pre- 

 viously described, so as to obtain data for computing the temperatures at 

 the various points every 5 or 10 minutes, as the rate of temperature change 

 seems to require. A few observations from an actual experiment are given 

 in table 3, in which are noted: First, the time; next, an occasional balancing 

 of the current; then the potentiometer readings for the various junctions, 

 each reading consisting of a setting and a deflection as already described. 

 After these follows an occasional reading of the Beckmann thermometer in 

 the constant-temperature oven. Finally a column is provided for miscella- 

 neous remarks, including observations for extraneous electromotive force, etc. 



Table 3. Body-temperature experiment. 

 Date: March 1, 1911. Subject: C. H. H. 



'Junction about 11 cm. deep in the rectum. -Junction about 7.5 cm. deep in the rectum. 

 COMPUTATIONS FOR THE EXPERIMENT. 



The method of obtaining the temperatures at the different locations and 

 times specified involves very much the same type of computation as that used 

 in calibrating. 1 The corrected potentiometer balance is obtained exactly as 

 in the calibration computations by adding two quantities to the setting: First, 

 the correction for extraneous electromotive force; and second, the deflection 

 which has been multiplied by a factor depending on the galvanometer sensi- 



>See p. 25, 



