ItO BULLETIN OF THE 



inches in diameter it did not give sufficient volume to again 

 reach the earth by spreading. 



In experiments of previous years the fact has been shown that 

 the sound is heard under certain conditions better when moving 

 against the wind than in the opposite direction. This was not- 

 ably the case in the experiments made at Sandy Hook in Sep- 

 tember, 1874, during which a sound from the west was heard with 

 the wind about three times as far as a sound from a similar source 

 was heard from the east, or against the wind ; and, again, the 

 same sound was heard from the west three times as far as from 

 the east after the wind had settled to a calm ; and in a third ob- 

 servation the same phenomenon was observed after the wind had 

 increased to a velocity of ten miles an hour from the east. 

 These effects were afterwards shown to be connected with the 

 fact that the wind during the whole day was blowing strongly 

 from the west, and that the apparent changes of the wind were 

 due to currents at the surface, and thus a sufficient explanation 

 was given to the phenomena observed. 



It would appear, however, from the investigations of last sum- 

 mer, that the wave of sound, which has been refracted upward, 

 may descend at a greater distance from its origin than even that 

 at which sound moving with the wind can be heard ; probably 

 involving a peculiar case of undulating or compound refraction; 

 but this requires further investigation. 



Each series of observations gives rise to new questions, and 

 indicates that the subject is one which is rich in new results. Un- 

 fortunately, however, the observations can only be made by the 

 aid of steamers ; and these, in the Lighthouse service, can only 

 occasionally be employed in the rare intervals of more impera- 

 tive duties. 



In order, however, to collect data for further use in the expli- 

 cation of the phenomena, the Light-keepers at B.lock Island and 

 Montauk Point (the eastern portion of Long Island) have been 

 directed to blow the fog-signals for an hour on every Monday 

 morning, each noting whether he can hear the sound from the 

 other station ; observing, at the same time, the direction of the 

 wind and the apparent motion of the clouds. 



From the result of these observations during the year it appears 

 that the clouds give frequent indications of adverse wind cur- 

 rents, and that the number of times that the sound has been 



