726 



SOUND-SIGNALS. 



which, absorbing and reflecting the sound, pro- 

 duced an atmosphere of acoustic opacity. 



In the mean time ship-masters were occa- 

 sionally bringing their ships to grief by placing 

 too much confidence in their hearing of the 

 fog-signals. Complaint would follow against 

 the signal-keeper, who would be charged with 

 having failed on that particular occasion to 

 operate his fog-signal. Thereupon the matter 

 would be investigated by a disinterested per- 

 son, usually an officer of the navy, and it would 

 generally be made to appear that the fault lay 

 not in the fog-signal, nor in the signal-keeper, 

 but in the audition by the mariner of the blast 

 the fog- signal made. 



In fact, these investigations have shown the 

 fallacy of the sailor's idea that sound is always 

 heard in all directions from its source, accord- 

 ing to its intensity or force, and according to 

 the distance of the hearer from it; and they 

 have also proved to the sailor, what was be- 

 fore known to the scientific world, that though 

 there may be no lack in the volume of the 

 sound emitted by the fog-signal, there may be 

 a decided lack in the audition of that sound ; 

 that it may not be heard at the intensity prop- 

 erly expected ; that it may not be heard at all 

 at the place expected ; that it may be heard 

 faintly where it ought to be heard loudly ; that 

 it may be heard loudly where it should be 

 heard faintly ; that it could not be heard at all 

 at some points within easy ear-shot ; and then 

 farther away it could be heard better than 

 near by ; that it could be heard and lost and 

 heard and lost again within reasonable hear- 

 ing distance, and all this while the signal was 

 in full blast and sounding continuously. 



A resume of certain of these investigations 

 made by disinterested officers of the Govern- 

 ment, showing their method and their results, 

 will make these statements more readily com- 

 prehended. 



On the night of Nov. 6, 1880, the steamer 

 Ehode Island was wrecked on Bonnet Point, 

 at the western entrance to Narragansett Bay, 

 when more than $1,000,000 was lost. The 

 cause of the disaster was alleged to be the 

 failure of Beaver Tail fog- signal (then a Daboll 

 trumpet) to sound its blast. This signal was 

 on the southern end of Conanicut island, which 

 divides the entrance of Narragansett Bay. The 

 western entrance is but If of a mile wide, with 

 rocky shores. Bonnet Point is but !$ mile 

 from Beaver Tail. As the fog-signal was gen- 

 erally heard at Newport, five miles distant, 

 and had been heard ten miles away, it seemed 

 almost self-evident that the fog-signal keeper 

 had failed to operate his machine when it could 

 not be heard on a steamer at Bonnet Point, or 

 even when she was in the middle of the chan- 

 nel not a mile away from the signal. But the 

 Lighthouse Board, as usual, caused investiga- 

 tion to precede action. An officer of the navy, 

 detailed to look into the matter, found copious 

 evidence that the fog-signal was in full blast 

 before, after, and during the disaster, and that 



it had been heard and acted on by other ves- 

 sels much farther off than the Rhode Island. 

 Then he took the testimony of the officers and 

 passengers of the ill-fated steamer, and found 

 it certain that they listened for and expected 

 to hear the fog-signal; that they practically 

 did not hear it, and the effect on them was the 

 same as if it had not been operated at all 

 Thereupon, on Nov. 16, 1880, ten days after 

 the wreck, he set the fog-signal going, though 

 it was on a clear, cold, sunny day, and ran 

 over in a sail-boat the course the Rhode Island 

 had taken, going to .the wreck itself, and then 

 ran out of the western channel up by the fog- 

 signal, through the eastern channel, by Castle 

 Hill and Fort Adams, to Newport. The result 

 is shown in Fig. 3, in which the intensity of 

 the sound as heard from the sail-boat is graphi- 

 cally indicated by the width of the track taken 

 by the boat. Where the line is widest, the 

 sound had the most volume ; where the line is 

 narrowest, the sound was the least ; where the 

 line is broken, the sound could not be heard at 

 all. The wind was moderate, from the west. 

 The observations began at 11.25 A. M. and oc- 

 cupied several hours. The result showed all 

 the aberrations of audition named as possible 

 in the preceding paragraph. 



In the summer of 1881, while on a light- 

 house steamer, the writer experienced some- 

 thing of the variations in the audition of sound 

 made by the Beaver Tnil fog-signal, then a ten- 

 inch steam whistle. When the steamer left 

 the landing at that lighthouse, the fog-signal 

 was to sound for a given time and to begin 

 when the steamer had reached a point about 

 half a mile distant. When that point was 

 reached, we could see from the steam-puffs 

 coming from the stack-pipe that the signal was 

 being blown ; but we could not hear it, nor 

 did we, as we continued on our course, running 

 at the rate of six miles an hour, for the next 

 five minutes. When near Whale Rock, slightly 

 less than a mile and a half from the signal, the 

 steamer's paddle-wheels were stopped, silence 

 was ordered fore and aft, and we all listened 

 intently. The expert naval officers thought 

 they heard a trace of the fog-signal, but my 

 untrained ears failed to differentiate it from 

 the moan of the whistling-buoy near Whale 

 Rock. Yet the blast of the ten-inch whistle 

 for which we were listening is often heard ten 

 miles away, with distinctness and certainty. 



Soon after I had another opportunity to ob- 

 serve the operations of this signal. We left 

 Narragansett Pier, R. I., on Aug. 6, 1881, at 4 

 p. M., in a dense fog, with a strong breeze from 

 the west-south w r est and a heavy chop sea. 

 We w r ished to ascertain how far the Beaver 

 Tail fog-signal conld be heard dead to wind- 

 ward, and in the heaviest of fogs. At Whale 

 Rock, one and one third mile from it, we did 

 not hear a trace of it; then the steamer was 

 headed directly for Beaver Tail Point, and we 

 ran slowly for it by the compass until the pilot 

 stopped the steamer, declaring we were almost 





