ATMOSPHERE AND THE ACOUSTIC EFFICIENCY OF FOG-SIGNAL MACHINERY. 2(J3 
No. 10. September 12, 1913. Table 10 and Chart 10. 
Note the poor transmissions against the direction of the wind (observations 1 to 11). That the signal 
was first heard from the bridge confirms the refraction theory. The abnormally low phonometer reading 
at the control station is difficult to account for except that the wind was in a direction such that the 
influence of the lighthouse and adjoining buildings in creating eddies in the immediate neighbourhood 
of the diaphone trumpet was greatest. The possibility of eddies in the immediate neighbourhood of 
a fog-signal apparatus having an abnormally great effect in attenuating sound-waves of large amplitude 
should be made the subject of a special investigation. 
No. 11. September 16, 1913. Table 11 and Chart 11. 
Note the very poor transmission against the direction of the wind (observations 1 to 13) with relatively 
good conditions of propagation in a direction at right angles. In order to see to what an extent the dis¬ 
tribution of sound was changed during a short interval of time, the same course inward and outward was 
repeated (observations 52 to 72). The curves show only a general resemblance. The effect of a wind in 
a direction opposite to that of the sound is very marked even at a distance as close as the end of Father 
Point wharf (1150 feet distant). 
