RESEARCHES IN SOUND. 497 



WJiiteJwad Ughf-sfafioii m on a small island abont a mile and a half 

 from the coast of ^Maine, on the western side of the entrance to Penob- 

 scot Bay, and in the direct line of the coasting-steamers and other ves- 

 sels from the westward bonnd into the Penobscot Bay and River. The 

 light-honse and fog-signal are situated on the southeast slope of the 

 island, the surface of which consists almost entirely of rock, the middle 

 being at an elevation of 75 feet above the mean tide-level. 



The phenomena which had been observed at this and other stations 

 along the coast consisted of great variation of intensity of sound while 

 approaching and receding from the station. As an example of this we 

 may state the experience of the observers on board the steamer City of. 

 Richmond on one occasion, during a thick fog in the night in 1872, The 

 vessel was approaching Whitehead from the southwestward, when, at a 

 distance of about six miles from the station, the fog-signal, which is a 

 10-inch steam-whistle, was distinctly perceived and continued to be 

 heard with increasing intensity of sound until within about three miles, 

 when the sound suddenly ceased to be heard, and was not perceived 

 again until the vessel approached within a quarter of a mile of the sta- 

 tion, although from conclusive evidence furnished by the keeper it was 

 shown that the signal had been sounding during the whole time. The 

 wind during this time was from the south, or approximately in an oppo- 

 site direction to the sound. Another fact connected with« this occur- 

 rence was that the keeper on the island distinctly heard the sound of 

 the whistle of the steamer, which was commenced to be blown as soon 

 as the whistle at the station ceased to be heard, in order to call the at- 

 tention of the keeper to what was supposed to be a neglect of his duty 

 in intermitting the operations of his signal. It should be observed in 

 this case that the sound from the steamer was produced by a G-incli 

 whistle, while that of the station was from an instrument of the same 

 kind of 10 inches in diameter; or, in other words, a lesser sound was 

 heard from the steamer, while a sound of greater volume was unheard 

 in an opposite direction from the station. It is evident that this result 

 could not be due to an 3^ mottled condition or want of acoustic transpar- 

 ency of the atmosphere, since this would absorb the sound equally in 

 both directions. The only plausible explanation of this phenomenon 

 is that which refers it to the action of the wind. In the case of the 

 sound from the steamer, the wind was favorable for its transmission, 

 and hence it is not strange that its sound should be heard on the island 

 when the sound from the other instrument could not be be heard on the 

 steamer. To explain on the same principle the fact of the hearing of 

 the sound at the distance of six miles, and afterward of losing it at the 

 distance of three miles, we have only to suppose that in the first in- 

 stance the retarding efiect of the wind was small, and tliat in the sec- 

 ond it became much greater on account of a sudden increase in the rel- 

 ative velocity of the current in the ui^per and lower portions. 



After malving a critical examination of the island and the position of 

 S. Mis. 59 32 



