34 TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY. 



at the calorimeter to a small constantan block A, and in the same way the 

 copper wire running to the calorimeter is soldered to a small copper block B. 

 These blocks are mounted on a hard-rubber base C, and are provided with 

 binding screws of constantan and copper, respectively, by means of which the 

 thermal junction may be connected to the circuit without the intervention 

 of any metal other than the two required for the thermometer itself. 



The thermometer consists of two wires 1.6 meters long, 0.0455 millimeters 

 in diameter, of constantan and copper respectively, well insulated, and soldered 

 together at one end D. At the other end the wires are screwed to two flat 

 terminals of constantan E and copper F, which are shaped to be received by 

 the binding screws already mentioned. These flat terminals are mounted 

 on a hard-rubber block G to which the wires are fastened in such away as to 

 make the joint absolutely rigid. The wires are covered by a 6.4 millimeter 

 rubber tube H down to some 25 centimeters from the junction itself; this 

 tube is protected by a spiral spring I at the point where it leaves the hard- 

 rubber block G. This comparatively heavy tubing is continued by a smaller 

 thin-walled rubber tube J for the remainder of the distance to the thermal 

 junction; this thin tubing fits tightly around the wires and is closed at the end 

 D by being tied tightly with silk. 



It should be remarked that considerable trouble has been experienced by 

 extraneous electromotive forces developed at the point where the constantan 

 wire from the thermal junction is soldered to the flat constantan terminal E. 

 This stray electromotive force has been found to be reduced practically to 

 zero when the soldered connection is replaced by a clamp connection, made 

 by fastening the wire under the head of a small constantan screw, without 

 the use of solder. Apparently in this case the electromotive force is due not 

 to difference in the constitution of the two pieces of metal, but rather to the 

 unbalanced effect of the constantan-solder and solder-constantan couples. 

 This leads to the conclusion that when it is necesary to solder two pieces of 

 metal of identical constitution together, stray electromotive forces will be 

 less likely to be developed if the two pieces have the same size and shape and 

 are surrounded by as nearly as possible the same conditions of heat loss. 



The operation of the apparatus is identical in procedure with the earlier 

 form. The current is first balanced, after which the potentiometer balance 

 is found, partly by setting, partly by deflection. Occasional observations 

 are also required of the temperature in the oven and the stray electromotive 

 force. 



