83 
tion that at short distances from the source the intensity of the sound 
varies as 
20+ 35), 
m2 72 
while at great distances from the source the intensity varies as 
9 . 
e 2m1 
2 
r 
In these formule 7 stands for the distance from the source, a for the 
velocity of sound, and » for the number of vibrations per second, while 
m is a constant that depends on viscosity conduction and radiation. 
In the previous paper the author described experiments made to find 
the value of m. The method was confessedly not altogether satisfactory. 
Later another method was devised and applied during the summer of 
1898. As before, the work was performed in the open air at a very quiet 
part of the River St. John, New Brunswick, Canada. The season was 
very unfavorable, and only the few results hereafter described were ob- 
tained. 
The greatest difficulty in such work is in finding a variable standard 
of intensity of the same pitch and quality as the sound studied. In the 
present case this was overcome by using the sound conveyed through a 
telephone as the standard, the transmitter being placed near the source 
of sound and the receiver held at such a distance from the ear that the 
. sound heard directly and that heard through the telephone were of equal 
intensity. Only one ear was used, the other being filled with wool and 
closely covered by a heavy pad. This use of a telephone receiver at dif- 
ferent distances from the ear as a standard implied a knowledge of the 
law of intensity of the sound at different distances from the receiver. 
This point, the law of intensity at short distances, was first tested by 
using the receiver in two states of intrinsic sensitiveness—first, shunted; 
second, not shunted. Now, if a series of sounds of different intensities 
(e. g., the sound of the same whistle differently deadened by coverings) 
be compared with these two standards, the ratio of the two intensities 
thus estimated for each sound should be the same for all the sounds, and 
if calculation according to the theoretical law above stated for short dis- 
tances should show such a constancy of ratio, it would afford strong 
evidence that the theoretical law is correct. The tables of results obtained 
