348 BULLETIN OF THE 



In 1872 it was observed from oa board a steamer approaching 

 Portland Head station in the harbor of Portland (Maine) that the 

 fog-signal which had been distinctly heard through many miles, 

 was lost to the ear when within two or three miles of the point, 

 that it continued inaudible throughout the nearer distance of a 

 mile or so, and that it was again heard as the station was neared. 

 At Whitehead light station on a small rocky island about a mile 

 and a half from the coast, (being some 65 miles northeast of Port- 

 land Head,) it was observed on board a steamer approaching the 

 station during a thick fog, that the signal (a 10-inch steam whistle) 

 though distinctly heard at the distance of six miles or more, and 

 with increasing distinctness as the steamer advanced, was suddenly 

 lost at about three miles, and was not recovered until within a 

 quarter of a mile from the station ; the wind at the time being ap- 

 proximately adverse to the sound. A six-inch steam whistle on 

 board the steamer was meanwhile distinctly heard at the station 

 during the whole time of inaudibility of the larger ten-inch whistle, 

 which had also been sounded without any interruption. This re- 

 markable phenomenon implied a compound flexure of the sound 

 beams, and accorded with previous observations made at the same 

 points by Gen. Duane the engineer in charge of the first and second 

 Light-house Districts. 



In 1873 observations were again made at Whitehead station, 

 and at Cape Elizabeth light station, both on the coast of Massa- 

 chusetts. At Whitehead the steam whistle was heard through a 

 distance of 15 miles, with a light adverse wind. At Cape Eliza- 

 beth, with a stronger adverse wind, the siren was heard only about 

 nine miles 



In 1874, observations were made at Little Gull Island (off the 

 coast of Connecticut); at Block Island, (off the coast of Rhode 

 Island); and at Sandy Hook (New Jersey). At Little Gull 

 Island the sound of a siren was heard against a moderate wind, 

 only three and a half miles. At Block Island the siren was reported 

 to have been heard under favoring conditions of wind through a 

 distance of more than 25 miles. While it was frequently heard at 

 Point Judith station, and the siren at the latter point was as fre- 

 quently heard at Block Island, (the distance between the two points 

 being 17 miles,) it was shown on comparison of records, that the 

 two instruments had not been heard simultaneously; the wind 

 when favorable to the one being unfavorable to the other. 



At Sandy Hook, for the purpose of making simultaneous ob- 

 servations in different directions, three steamers (the tenders of 

 different light-houses) were employed, with steam whistles specially 

 adjusted to the same tone and power. The latter quality having 

 been carefully tested by the phonometer, the three vessels steamed 

 out abreast on trial ; and their whistles sounding in regular suc- 

 cession " became inaudible all very nearly at the same moment." 

 One of the vessels being then anchored at a distance from land, 



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