EESEARCHES IN SOUND. 543 



tlie wind than in a contrary direction. We think however that these 

 instances are generally followed by a change in the direction of the wind 

 at the snrface of the earth. 

 Light-House Board, October, 1875. 



PART Y.— INVESTIGATIONS IN 1877.* 



On account of the occurrence of the Centennial Exhibition, which 

 absorbed most of the time of the officers of the Light-House Board not 

 devoted to ordinary light-house service, but few observations were made 

 relative to sound in 187G, and an account of what were made is incor- 

 porated in the following report. 



Agreeably to previous engagement, I visited Portland, Me., to make 

 some investigation in regard to an abnormal phenomenon of sound, 

 which was noticed in a former report. We left Portland on the after- 

 noon of September 3, 1877, in the steamer Iris, which had been fitted up 

 during the year under the direction of the inspector. Commander H. F. 

 Picking, and was in excellent condition, and well adapted to the duty 

 of a light-house tender. The party consisted of General J. C. Duane, 

 engineer of the first district ; Commander H. F. Picking, inspector of 

 the first district ; Mr. Edward L. Woodruff, assistant engineer of the 

 third district ; Mr. Charles Edwards, assistant engineer ot the first dis- 

 trict, and myself. 



We first examined one of the automatic whistling-buoys invented by 

 Mr. Courtenay, of New York. This was in place and emitting sounds 

 at a station called Old Anthony, oft' Cape Elizabeth, about nine miles 

 from Portland. On approaching it at right angles to the direction of 

 the wind, we heard it at the distance of a mile. But the sound did not 

 appear loud even within a few rods. It was however of considerable 

 quantity, being from a locomotive whistle of ten inches in diameter. 

 The instrument is operated by the oscillation of the waves, which at 

 this time were not of sufficient height to move it vertically through a 

 space of more than one foot. It emitted a sound at each oscillation. 

 This invention consists of a large pear-shaped buoy about twelve feet in 

 diameter at the water-surface, and floats about twelve feet above the 

 same jilane. In the interior of this buoy is a large tube or hollow cyl- 

 inder, three feet in diameter, extending from the top through the bottom 

 to a depth of about thirty feet below the latter. This tube is open at 

 the bottom, but projects air-tight through the upper part of the buoy, 

 and is closed with a plate having three orifices in it, two for letting in 

 the air into the tube, and one between the others for letting it out to 

 operate the whistle. These orifices are connected with three tubes 

 which extend downward to near the level of the water, where they pass 

 through a diaphragm which divides the cylinder into two parts. 



* From the Report of tlio Light-House Board for 1877. 



