576 



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 



