Aberrations of Audibility of Fog Signals: A Paper Read Before the Philosophical Society of Washington, October 22, 1881

Front Cover
Judd & Detweiler, 1882 - Fog-signals - 15 pages
 

What people are saying - Write a review

We haven't found any reviews in the usual places.

Selected pages

Other editions - View all

Common terms and phrases

Popular passages

Page 34 - With a view to the protection of life and property at sea, in the years 1873 and 1874, this subject received an exhaustive examination, observational and experimental. The investigation was conducted at the expense of the Government, and under the auspices of the Elder Brethren of the Trinity House [the governing body of the British Light-House Establishment.] " The most conflicting results were at first obtained.
Page 34 - ... 9^ miles; on the 1st of July 12żż miles; on the 2d 4 miles, while on the 3d, with a clear, calm atmosphere and smooth sea, it was less than 3 miles...
Page 36 - ... as before, or because he does not hear it at all. ' ' He should not assume that the fog-signal has ceased sounding because he fails to hear it even when within easy earshot. " He should not assume that the aberrations of audibility which pertain to any one fog-signal pertain to any other fog-signal. " He should not expect to hear a fog-signal as well when the upper and lower currents of air run in different directions; that is, when his upper sails fill and his lower sails flap; or when his lower...
Page 30 - Island, and until he was within half a mile of the siren which was in full operation. On the next morning our steamer anchored about a mile north of Little Gull ; the wind was light, the air was clear, and the day was warm and beautiful. As it had been preceded by a warm night the atmosphere was homogeneous, and it was expected that we should have a day of normal audition and barren of curious phenomena. After the siren had commenced its noise we ran down to a point within half a mile of the light-house,...
Page 33 - The most perplexing difficulty, however, arises from the fact that the signal often appears to be surrounded by a belt, varying in radius from one to one and a half miles, from which the sound appears to be entirely absent. Thus, in moving directly from a station, the sound is audible for the distance of a mile, is then lost for about the same distance, After which it is again distinctly heard for a long time.
Page 30 - ... any fog-signal. When the fog-trumpet was set up at Beaver Tail Point in 1856, the Naval Secretary of the Board, then Lieutenant, now Rear Admiral Jenkins, USN, in company with Mr. Daboll, its inventor, found, in returning to Newport, that they lost the sound of the signal between Beaver Tail and Fort Adams, and recovered it again between the Fort and Newport, as did later observers, and that this failure to hear it did not result from any failure of the signal to operate. The Board's publications...
Page 26 - Light, was not in operation at the time of the accident, and the Light-House Board, also, as usual, immediately ordered an investigation. This was made by the Assistant Inspector of the Light-House District, a naval officer, who reported that after taking the sworn evidence of the light-keepers at Little Gull and the other light-stations within hearing distance, of other Government officers who were, for the time being, so located that they might have had knowledge of the facts, and of the officers...
Page 36 - He should not expect to hear a fog-signal well when the sound must reach him over land, as over a point or an island. And, when there is a bluff behind the fog-signal, he should be prepared for irregular intervals in audition, such as might be produced could the sound ricochet from the trumpet, as a ball would from a cannon ; that is, he might hear it at 2, 4, 6, 8 and 10 miles from the signal, and lose it at 1, 3, 5, 7, 9 and 11 miles distance, or at any other combination of distances, regular or...
Page 30 - N. , force j, and steady throughout. Day clear and beautiful. The Light House Board has known from the first that aberrations in audibility might occur near any fog-signal. When the fog-trumpet was set up at Beaver Tail Point in 1856, the Naval Secretary of the Board, then Lieutenant, now Rear Admiral Jenkins, USN, in company with Mr. Daboll, its inventor, found, in returning to Newport, that they lost the sound of the signal between Beaver Tail and Fort Adams, and recovered it again between the...
Page 33 - ... with no perceptible difference in the state of the atmosphere. " The signal is often heard at a great distance in one direction, while in another it will be scarcely audible at the distance of a mile. This is not the effect of wind, as...

Bibliographic information