256 DR. LOUIS YESSOT KING ON THE PROPAGATION OF SOUND IN THE FREE 
Air temperature was measured by means of a self-registering thermometer. With the kind permission 
of Dr. H. T. Barnes, Director of the Macdonald Physics Building, one of his self-recording marine 
thermometers was installed for the purpose of taking sea temperatures. No direct effect of sea 
temperatures on sound transmission could be detected, however, so that it has not been thought 
necessary to reproduce these records. Mr. Hemming took charge of wind observations with the only 
apparatus available, a small anemometer consisting of a fan whose revolutions could be timed by means 
of a stop-watch. With this instrument the velocity of the wind relative to the ship was obtained. The 
direction of the wind relative to the ship was observed from the direction of the ship’s smoke. The 
ship’s speed and the magnetic bearing of the course was noted at the same time. By the usual graphical 
construction the velocity and direction of the wind relative to the earth’s surface was determined. In 
each of the Charts 1 to 14, the wind velocities at the positions where they were observed are shown in 
magnitude and direction by arrows, the numbers beside them indicating A’elocities in statute miles per 
hour. In future observations of this kind the use of self-registering instruments for wind velocity and 
direction is recommended. 
While phonometer readings were taken at intervals of one minute by the writer, the position of the 
ship was determined by Mr. Hemming from sextant observations of the angles subtended by landmarks 
of known position on shore. Both sets of observations were carefully timed so that the position of the ship 
at each signal could be plotted down with fair accuracy on a chart of the locality. At each position thus 
determined an ordinate was drawn perpendicular to the line representing the ship’s course, proportional 
to the phonometer reading, and hence to the pressure amplitude in the wave. In this way is obtained a 
graphical representation of the variation of sound amplitude along various courses in the neighbourhood 
of the fog-signal station. It must be kept in mind that the results thus obtained do not represent the 
state of affairs existing at the same instant, but show variations of amplitude in sequence of time. Each 
phonometer reading was identified by a position number entered on each of the Charts 1 to 14, opposite 
the position of the ship at the instant of observation. The corresponding phonometer observations are 
entered in Tables 1 to 14, together with meteorological observations and remarks. 
(ii.) Description of Tables and Charts. 
No. 1 .—Short Bunge Acoustic Survey, September 3, 1913. Table 1 and Chart 1. 
A preliminary survey of conditions of sound propagation in the immediate neighbourhood of the 
fog-signal station was carried out by means of the Webster phonometer, with a view to obtaining some 
light on the extent of the large atmospheric losses believed to occur in this region. As a first step, 
observation stations were marked out at intervals of 50 feet along eight lines radiating from the resonator 
of the diaphone, making angles of approximately 45 degrees with one another. At the same time 
topographical observations were carried out, from which a map of the locality could be drawn giving the 
positions of the various buildings and of the shore line on the seaward side. Observations from which 
the contour lines of the beach were drawn were carried out by Mr. Hemming. These are shown in 
Chart 1 drawn from the data thus obtained. The contour line 1 is the high tide level of September 2, 
1913, and is 14 feet below the level of the diaphone resonator. Successive contour lines 1, 2, 3, 4, &c., 
represent differences of level of 1 foot. 
Observations were carried out on September 2, 1913, the day having been chosen on account of the 
comparatively calm conditions then prevailing. The phonometer was mounted on a theodolite tripod as 
shown in Plate 1 and tuned to resonator position 8 throughout. The observations were taken almost 
continuously between 10.30 a.m. and 4 p.m., and are entered in Table 1 in chronological order. Along 
each of the lines (numbered I. to VIII.) phonometer readings were taken at each observation station and 
numbered, commencing with No. 1, 50 feet distant from the diaphone : the readings were repeated at 
each station on the way back. No difficulty was experienced in setting up the phonometer at each 
