268 DK. LOUIS VESSOT KING ON THE PROPAGATION OF SOUND IN THE FREE 
Table I. 
Date and remarks. 
R. 
Observation 
numbers. 
[*] 
Energy flux 
in solid angle. 
Theoretical 
energy flux. 
No. 6. September 4, 1913 . 
(feet) 
3040 
3-12 
14-22 
(mm.) 2 
1-205 
0-74 
watts. 
0-07 
0-04 
watts. 
0 = 50“ 86 = 40/6080 . 
Acoustic output = 1'2 H.P. . 
6080 
45-56 
62-76 
1-73 
1-24 
0-39 
0-28 
1-63 
No. 9. September 10, 1913 . 
2600 
45-60 
3-72 
0-18 
<f> = 60° 86 = -40/6080 . 
5100 
8-35 
o-io 
0-02 
2-61 
Acoustic output = 1 • 6 H.P. . 
' 
No. 12. September 17, 1913 . 
3500 
7-17 
25-38 
3-20 
1-27 
0-24 
o-io 
• 
</> = 50“ 86 = 40/6080 . 
7000 
48-63 
0-43 
0-13 
2-31 
Acoustic output = 1-7 H.P. . 
No. 13. September 19, 1913 . 
3040 
65-75 
4-98 
0-33 
</. = 60’ 86 = 40/6080 . 
6080 
6-20 
0-66 
0-18 
2-77 
Acoustic output = 1 • 7 H.P. . 
12160 
28-48 
0-46 
0-49 
No. 14. September 20, 1913 . 
4000 
74-96 
1-44 
0-17 
= 60° 86 = 40/6080 . 
— 
— 
— 
— 
2-77 
Acoustic output = 1 ■ 7 H.P . 
The above table shows in several cases that the energy flux in the same solid angle is in some cases 
greater at 1 mile than at | mile (No. 6), and in one instance (No. 13) considerably greater at 2 miles than 
at either 1 mile or £ mile. According to the inverse-square law of sound jiropagation, these estimates 
should be the same. We are obliged to conclude that contributions to the energy flux at these greater 
distances are made by refraction or by reflection from the upper regions of the atmosphere, and to some 
extent, possibly, by the sound scattered by atmospheric eddies reaching the observer from all directions. 
A comparison of the last two columns of Table I. shows that within the half-mile radius a large 
proportion of the energy is lost, confirming the conclusion already made as to the comparatively small 
atmospheric losses beyond this distance. 
(iv.) Note on Acoustic Shadows. 
During the course of the acoustic surveys several opportunities offered of observing the effects of 
obstacles in giving rise to acoustic shadows. 
On September 2, 1913 (see Chart 1), phonometer observations were taken on both sides of the wharf 
