10 A BICYCLE ERGOMETER WITH AN ELECTRIC BRAKE 



theoretical considerations, as will be shown in the third section, this was 

 not what would be expected; it appeared desirable, therefore, to repeat 

 the calibrations with a more delicate respiration calorimeter subsequently 

 constructed in the Nutrition Laboratory at Boston. Through the cour- 

 tesy of Dr. C. F. Langworthy, of the U. S. Department of Agriculture, 

 Washington, D. C, the original bicycle ergometer was sent to Boston 

 and installed inside the respiration chamber, fitted with a crank-shaft, 

 motor, belting, and shafting, and rotated at the varying rates of speed 

 formerly used. The range of speed was then considerably altered so as 

 to secure a rate of revolution of the pedals as low as 11 and as high as 120 

 per minute. 



When the new bicycle ergometer, constructed in the mechanical de- 

 partment of the Nutrition Laboratory, had been completed, it was sub- 

 jected to similar calibration tests, so that we now have an extensive series 

 of calibration tests with two ergometers of this type, built some 10 or 12 

 years apart, having different electro-magnets and yet embodying the same 

 fundamental principle. The next section of this report gives an account 

 of these calibration tests, while in the third section a study is made of 

 the magnetic reactions that take place when the disks of these instru- 

 ments are in rotation. 



