A. M. Mayer — Researches in Acoustics. 



89 



the currents of cold air in the balance-case, which are pro- 

 duced by the constant descent of air from the sides of the 

 cool vessel. 



The Apparatus in which the bars were heated and cooled. On 

 the precautions used so that one is sure of having the real 

 temperature of the bar when it is vibrated. 



The apparatus used to heat and cool the bar is shown in 

 fig. 3. In a brass box, C, is inclosed a box, C, containing the 



r 



N 



T 



3B 



bar, B, supported on its modes, N, N", by threads held by 

 upright rods. From this central box two tubes, T, P, pass 

 through the outer box C. The inner box is made water-tight 

 and steam tight by a rubber washer which is pressed between 

 the top of the box and its cover by means of screws. Through 

 the tube, T, the bar is vibrated by letting fall upon its center 

 a rubber ball fastened to a light wooden rod. On the blow of 

 the ball it rebounds and the rod is caught by the fingers in its 

 upward motion. The cork is then at once replaced in the 



