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SOUND-SIGNALS. 



although the fog-signal was heard at Mystic, 

 fifteen miles distant in another direction, and 

 although it was heard on a steam-tug a mile 

 beyond the Galatea, it was heard faintly, if at 

 all, on that vessel ; and if heard at all, was so 

 heard as to be misleading, though the Galatea 

 was but one eighth of a mile from the source 

 of the sound. 



It appears that this officer spent several days 

 steaming around Little Gull, while the fog- 



CON8TELLATION RK. 

 BREESE RK.* 



FIG. 4. 



This diagram shows the result of fog-signal tests at Little Gull 

 Island, Long Island Sound, July 11, 1881. Time, 10 A.M. 

 Wind, N. N. E. ; force, 2. Barometer, 29-77. Thermome- 

 ter, 61 Fahr. Weather at beginning, dark, overcast, with 

 squalls of Scottish mist from N. N. E. It began to clear at 

 11.80 A. M. 



signal was in full blast, in various kinds of 

 weather, and that he found the aberrations in 

 audition here were as numerous and even more 

 eccentric than those before mentioned as ex- 



FIG. 5. 



This diagram shows the result of observations at Little Gull 

 Island, Long Island Sound, July 15, 1881, beginning at 6.30 

 A. M. Thermometer, 59 Fahr. Barometer, 29 '80. Wind, 

 W. N. W. ; force, 3, hauling westward and increasing grad- 

 ually. 



perienced at Beaver Tail. The results of his 

 observations are given in Figs. 4 and 5, and in 



each case the condition of the atmosphere as 

 to humidity, pressure, temperature, and motion 

 are shown, as is also the tidal condition. 



On August 3d the writer had an opportunity 

 to hear this fog-signal and to note its audibil- 

 ity. The wind was from the south and very 

 light ; the air was damp, smoky, hazy, and, as 

 the sailors say, hung low ; the barometer stood 

 at 29-90 ; the tide was about flood. Our steam- 

 er was run for six miles in the axis of the 

 siren's trumpet, which was sounded for our 

 benefit at its full force. Note was made every 

 third minute in a scale of ten of the intensity 

 of the sound, and it was found that the audi- 

 tion decreased normally with the distance for 

 the first two miles; at 2J miles it had fallen 

 off one half; at 3 miles it had fallen off to one 

 tenth of its power ; at 3 miles away we could 

 hear but a faint murmur, and, when 4 miles 

 distant, we had lost it completely ; and yet 

 there seemed to be no reason why we should 

 not have heard it clearly at three times that 

 distance. 



The next morning was calm, but heavy with 

 white fog; yet we heard the Little Gull siren 

 distinctly, though it was 10 miles off, as we 

 lay at our wharf in New London. The steam- 

 er ran out of the harbor, but was compelled 

 to anchor, so thick was the fog ; yet we heard 

 Little Gull, though 7i miles off, at a force of 

 six in the scale of ten, and the sound was so 

 distinct that we could differentiate it from the 

 siren at the New London light, which was 

 much nearer to us. The steamer worked round 

 to inspect the neighboring lights, and we heard 

 the Little Gull siren when at North Dumpling 

 light station, Y miles off, at a force of six ; at 

 Morgan's Point Light, 10 miles off, at a force 

 of five; and we continued to hear it at an in- 

 tensity of from five to six as we worked around 

 among the other lights, within a compass of 10 

 miles, till the fog broke and the siren ceased. 



Opportunity soon occurred for making more 

 critical experiments. On a fine day we ran out 

 to Little Gull, had the siren started under full 

 steam, and then, following out a pre-arranged 

 programme, ran around Little Gull island in 

 such way as to describe a rectangle of about 

 eight by ten miles, its longest side running near- 

 ly north and south. No fixed rate of speed was 

 maintained, but the steamer slowed, backed, or 

 stopped, as was necessary. The atmosphere 

 was what the sailors call lumpy, and Prof. 

 Tyndall calls non-homogeneous. Prof. Henry, . 

 when writing of a like condition, said, "As 

 the heat of the sun increases during the first 

 part of the day, the temperature of the land 

 rises above that of the sea, and this excess of 

 the temperature produces upward currents of 

 air, disturbing the general flow of wind, both 

 at the surface of the sea and at an elevation 

 above." Observations were made and noted 

 in a scale of ten, of the force or intensity of the 

 signal's sound as it reached us at the end of 

 each minute. The diagram, Fig. 6, shows a 

 sufficient number of the results for our pur- 





