CALIBRATION TESTS 



19 



as before, both the earlier calibrations with this ergometer and those of 

 1911. The speed varied from 39 to 153 revolutions, the circles indicating, 

 as before, the earlier observations, and the small crosses those that have 

 recently been made. The plotting of these points shows a sharply de- 

 fined curve with a striking dissimilarity between the rate of revolution 

 and the heat production per revolution. This distinctly contradicts 

 the statement previously made that the heat per revolution was independ- 

 ent of the rate of speed. With a low rate of speed, the heat per revolu- 

 tion is likewise low, rises to a maximum when the speed is not far from 60 



.018 



.017 



.016 



015 



.014 



.013 



.01 2 



o 



v 



XX. 



3^_ 



30 40 50 60 70 80 90 lOO IIO 120 130 140 150 



Fig. 5. Calibration curve of ergometer I for magnetizing current of 0.9 ampere. 



x 



.022 



.021 



.020 



.019 



.018 



.017 



30 40 50 60 70 80 90 lOO HO 120 



Fig. 6. Calibration curve of ergometer I for magnetizing current of 1.1 amperes. 



to 80 revolutions per minute, and gradually falls off with increasing speed 

 until, with a speed of 153 revolutions per minute, it is even lower than 

 at the very low rate of 39 revolutions per minute. It is of especial im- 

 portance to note that the top of the curve is obtained when the speed is 

 from 55 to 80 revolutions per minute. 



Since it was highly improbable that all subjects would wish to ride the 

 bicycle ergometer with exactly the same degree of resistance, the cal- 

 ibrations were made so extensive as to cover practically all of the different 



