Dr. A. M. Mayer's Researches in Acoustics. 267 



The bevelled face of the driving-wheel of the rotator has 

 three grooves cut in it, in steps. Corresponding grooves are 

 cut in the pulley of the axle. 



To run a rotator of this description smoothly, without jars 

 or vibrations, it is necessary that the cord which passes over 

 the driving-wheel and pulley should be very flexible and 

 have a circular section of uniform area throughout its length. 



Fiar. 7. 



I obtained such a cord by soaking a cord of porpoise leather 

 in neat's-foot oil, and then drawing it many times through 

 wire-drawing plates. The ends of the cord are connected by 

 a short hook-and-eye coupling. The driving-wheel can be 

 slipped up or down the standard of the rotator to adjust the 

 tension of the cord. 



The driving-wheel is turned by a handle of aluminium of 

 the form shown in the figure. It is necessary to have a 

 handle of small diameter in order to turn the wheel with a 

 uniform velocity. The fingers which clasped the handle were 

 coated with plumbago dust. 



