550 



Prof. H. L, Callendar on Electrical 



determined accurately, as the temperature was not perfectly 

 steady, but it was probably less than a tenth of a degree,, 

 and therefore insufficient to account for the observed lag. 

 With the flat platinum tube thermometer, owing to its much 

 larger surface, the heating effect of the current was far too 

 small to be appreciable on the scale of the records. 



That the apparent lag of the thermometer is really due to 

 the slowness of recovery of the temperature of the mouth 

 itself after being cooled in any manner, is further shown by 

 the following records taken with the platinum tube thermo- 

 meter under different conditions. The first curve, marked 

 (1) in fig. 4 was taken at the conclusion of an ordinary 



Fig. 4. 



Platinum Tube Thermometer Records in Mouth after different 

 periods of closure. 



conversation, without any precautions as to keeping the 

 mouth closed or refraining from speaking, until the thermo- 

 meter had been inserted. The thermometer did not reach 

 32° C. for more than a minute, and was still nearly 1° CL 

 below the normal temperature after a lapse of seven minutes. 

 Curve No. (2) represents the record obtained after keeping 



