RESEARCHES IN SOUND. 501 



There is moreover at this station a bell, operated by a Stevens clock, 

 not at present nsed. It is placed on a high, wooden frame-structure, on 

 which one of tlie ancient bell-striking machines was originally erected. 

 The most iiroper position for the fog-signal is on the ground occupied by 

 this bell-tower, but as this was not removed at the time of the erection 

 of the trumpets, they were placed in such positions as to have the line 

 of sound interrupted to the northeastward by the bell and light towers. 

 It was therefore thought probable that this was the cause of tlie de- 

 ficiency of sound in this direction. To test this the vessel was caused 

 to traverse the arcs of several concentric circles, in the i^ortion of the 

 horizon where the sound was most required as a signal. The first arc 

 traversed was about one and one-half miles from the signal. The vessel 

 on this crossed the axis where the sound was quite loud, and proceeded 

 northward until the sight of the trumpet was obscured by the before- 

 mentioned towers, when the sound became almost inaudible. The ves- 

 sel next returned across the axis, on a circle of about three miles radius, 

 with similar results ; but after crossing the axis the sound on the south- 

 ern side continued to be but little diminished in intensity along an arc of 

 two and a half miles, or as far as the land would allow the vessel to go. 

 The vessel was next put upon an arc, of which the radius was qpe and 

 a half miles, and on the south side of the axis, and sailed to the north- 

 ward until the axis was reached, it was then turned and ran for the en- 

 trance of the harbor, hugging the southern shore, keeping as far from the 

 signal as possible. Throughout this passage the sound was clear and 

 loud, sliowing very little, if any, diminution of power as the several posi- 

 tions deviated more and more from the direction of the axis, until the 

 vessel was at right angles with the axis, the land not permitting any 

 greater distance. The vessel approached to within three-ciuarters of a 

 mile of the signal and then continued still farther around, until nearly in 

 the rear of it, the sound still continuing clear and loud. The vessel next 

 proceeded up the harbor, nearly in the line of the axis of the trumpet 

 prolonged in the rear, still continuing to hear the signal distinctly until 

 the keeper, losing sight of the vessel, stopped sounding the instrument. 

 These observations w^ere made nnder very favorable circumstances, it 

 being nearly calm. What wind did exist was about equally favorable 

 to points on either side of the axis. The inference from these observa- 

 tions is, first, that small objects placed near the source of sound tend to 

 diminish its intensitj'' in the direction of its interruption, and should, 

 therefore, if possible, be removed, or the instrument so placed as to ob- 

 viate such obstructions; and, second, that, even with the trumpet, the 

 sound so diverges from the axis as to be efficient even in the rear of the 

 instrument. 



Observations on Fog-Signals, August 25, 1874. 



The first of these was on board the steamer Putnam, at Little Gull 

 Island, with Admiral Trenchard, insi)ector of lights of the third dis- 



