from these two agree in a remarkable manner. Of the eight results the largest is 4896.21 feet, or 1492.37 metres per second, while the smallest is 4896.oo feet, or I492.3o metres per second. Corresponding values from the first explosion are 49o2. 3 feet, or I494.2 metres per second.
The intervals between the advent of the waves at the several hydrophones were used to calculate the speed of the sound over the distances separating these receiving instruments. For the second and third explosions the results obtained were 4895.1 feet per second and I492.1 per second. The discrepancy between the values furnished by the first detonation, on the one hand, and the second and third, on the other, was felt to require an explanation. A partial one was found to lie in the fact " that at the time bomb No. I was fired there was a fairly strong tidal current running in the direction of sound propagation, while several hours later when bombs No. 2 and No. 3 were fired the tide was practically at a standstill."
Since there are now methods of measuring the depth of the ocean that depend on an accurate knowledge of the speed of sound in water, the practical value of the above measurements is obvious.
G. F. S.