Page:Popular Science Monthly Volume 88.djvu/604

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��Popular Science Monthly

��should be noted that the mere presence of fog has little, if any- thing, to do with the eccentric behavior of fog-signals. That these acoustic caprices are asso- ciated in the popular mind with fog, and often attributed there- to, is due merely to the fact that, except for experimental pur- poses, fog-signals are only operat- ed in foggy weather.)

On the accompanying chart the thickness of the line representing Chadwick's route shows the varying degree of audibility of the signal at Beaver Tail Point. The sudden fading away of the sound within a short distance of the signal was, in this case, partly the result of topography (abruptly rising ground behind the signal), and therefore a per- manent condition; yet investigations

���Brenton's Reel .LlgM Vessel

Bell and Horn

��Nautical Miles

��tf*T

��f V"'i"'l"V."/ • •-;■

�� ��With the fogometer, here shown, both radio and sound signals are

used in determining a vessel's position in relation to the lighthouse,

thus obtaining more accurate results

��Narragansett Bay, the black lines showing how the audibility of a fog-horn fluctuated

��made on another da\, with different at- mospheric conditions, would doubtless have yielded results differing to a large extent from those here shown. . . Refraction, by the wind and by strata ., " of different densi- ties in the atmos- phere, undoubt- edly plays an im- - " - portant part in

the anomalous be- havior of fog-sig- nals; but thesub- j e c t is still obscu re, notwith- standing the elab- orate investiga- tions that have been devoted to it by Stokes, Tyn- dall, Henry, Rey- nolds, Rayleigh, and many others. The net result of the facts above set forth is that aerial fog-signals serve merely as a poor makeshift, pending the gen- eral adoption of submarine sig- nals. Radio sig- nals are also use- ful in this con- nection.

A device for utilizing both ra- dio and sound sig- nals to determine

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