334 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



The last column of this table gives the logarithmic decrement per 

 complete oscillation. The value .32, including the Joulean decrement 



.»0 .. /., 1.00 I.JO 



A/ Am 

 Figure 4. Resonance curve used in obtaining logarithmic decrement. 



as well as the radiation decrement, is 40 per cent higher than the 

 logarithmic decrement due to radiation alone, as computed by 

 Abraham's formula for the decrement, which is 



8 = 



9.74 



A 1 2l 



4l0g eT 



= .23 



The value of the decrement is, however, too small to produce a change 

 in the measured value of the wave-length by more than a small fraction 

 of one per cent. 



Summary of Results. — Assuming that the wave-length produced by 

 the parallel-wire oscillator is four times the length of one of the wires, 

 the wave-length produced by the fundamental electrical vibration of a 

 long, thin, rectilinear Hertz oscillator was found to be 2.094 times the 



