16 



A BICYCLE ERGOMETER WITH AN ELECTRIC BRAKE 



is necessary for the changes in temperature of the calorimeter. Since an 

 increase or decrease in temperature indicates a storage or loss of heat, 

 it is necessary to add or subtract the heat thus stored or lost to find the 

 amount of heat actually produced during the experimental period. The 

 heat produced by the current passing through the magnet amounted to 

 10.9 calories per hour, the third and fourth periods in the table being re- 

 spectively 1 minute shorter and 1 minute longer than the hour, thus ac- 

 counting for the slight variations from the average. The total heat 

 produced, then, is the heat measured, corrected for the changes in tem- 

 perature of the calorimeter and for the heat produced by the magnetizing 

 current. The records of the total number of revolutions per hour as 

 obtained from the revolution counter are given, together with the num- 

 ber of revolutions per minute. The final column indicates the number of 

 calories of heat produced per revolution of the pedals. 



Table 2. Results of calibration test of ergotneter I, July 7, 1911. 



[Current in ergometer magnet, 1.25 amperes.] 



Duration of period. 



10 h 22 m a.m. to ll h 22 m a.m. 



11 22 



12 22 



a.m. to 12 



22 

 21 

 22 



p.m. to 

 p.m. to 

 p.m. to 

 p.m. to 



22 

 22 

 21 

 22 

 22 



p.m. . 

 p.m. . 

 p.m. 1 

 p.m. 2 

 p.m. . 



10 22 a.m to 4 22 p.m. 



Corr. 



temp. 



diff. 



C. 

 3.05 

 3.12 



3.05 

 3.13 

 3.17 

 3.14 



3.11 



Duration of period. 



10 h 22 m a.m 



11 22 a.m 



12 22 



1 22 



2 21 



3 22 



p.m. to 

 p.m. to 

 p.m. to 

 p.m. to 



to ll h 22 m a.m. 

 to 12 22 p.m , 



1 22 



2 21 



3 22 



4 22 



p.m. 

 p.m. 1 

 p.m. 2 

 p.m. 



10 22 a.m. to 4 22 p.m 



Heat per 

 revolu- 

 tion. 



cal. 

 0.0225 

 .0228 

 .0225 

 .0228 

 .0226 

 .0226 



.0226 



i 59 minutes long. 2 61 minutes long. 



During the experiment of July 7, 1911, the heat per revolution of the 

 pedals ranged only from 0.0225 to 0.0228 calorie per revolution, the 

 average for the whole experiment being 0.0226 calorie per revolution. 

 The average number of revolutions during the test was 71.1 per minute. 

 With this ergometer, therefore, with a current of 1.25 amperes through the 

 magnet, it can be stated that at this speed each revolution results in 

 the development of 0.0226 calorie. 



