382 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



vided with a conical sound-collector 29 cm. in diameter, was placed at 

 a distance of about 1.5 meters from the organ-pipe. The 16 ohm prim- 

 ary and the 720 ohm secondary of the transformer, Figure 2, were em- 

 ployed. The galvanometer G was a d' Arson val type and had a resistance 

 of 538 ohms, and gave a throw of one scale division (A inch) for a 

 current of 1.53 X 10"^ amperes. 



The condenser C, Figure 2, having a total capacity of 1 microfarad, 

 and adjustable by steps of .05 microfarads, was given various values, 

 and the corresponding throws of the galvanometer when the pipe 

 was sounded were taken. In taking these readings the pipe was left 

 sounding until the coil of the galvanometer had completed its swing. 



The results are recorded in Table I. 



TABLE I. 



Adjustment of Electric Circcit to Resonance with 

 Sound Frequency. 



The curve of Figure 3 is plotted from the data of Table I. The hori- 

 zontal dotted line through the figure is the current with the condenser 

 short-circuited. This curve gives an idea of the advantage obtained 

 by the use of the proper capacity in the primary circuit of Figure 2. 

 The maximum of the curve shows a value of the current that is 

 nearly eight times the current obtained when the condenser was 

 short-circuited. 



