436 WRITINGS OF JOSEPH HENRY. fl874 



of a perpendicular cliff, at an elevation of from 75 to 100 feet 

 above the ocean, and furthermore that the direction of the 

 wind formed an angle of about 35° with the axis of the trum- 

 pet. Now the loudness of this echo was not the greatest at 

 the siren-house, but increased in intensity until a point was 

 reached several hundred yards from the trumpet, approxi- 

 mately more in accordance with a reflection from the waves. 

 The wind was blowing from the shore with the direction of 

 the sound as it went off from the trumpet, and nearly against 

 it on the return of the echo. I have attributed this phenom- 

 enon (which was first observed in 1866 at East Quoddy Head, 

 on the coast of Maine, and since at various stations, at which 

 the trumpet or siren has been used,) to the reflection of the 

 sound from the crests and slopes of the waves, and the obser- 

 vation we have mentioned would appear to favor this hypoth- 

 esis. In connection with this explanation, I may mention that 

 my attention has been called by General M. C. Meigs, of the 

 United States Army, to an echo from the palings of a fence, 

 and also from a series of indentations across the under side 

 of the arch of one of the aqueduct bridges of the Washing- 

 ton water-works. The fact that the sound was much louder 

 at a point considerably distant from the trumpet was noted 

 by one of the party entirely unacquainted with the hypoth- 

 esis. 



The keeper of this station confirmed (without a leading 

 question) the statement of Captain Keeney, that a feeble 

 sound of a distant object — as the roar of the surf, can fre- 

 quently be heard against the direction of the wind, and 

 that in this case it always betokens a change in the 

 weather, and is in fact used generally by the fishermen as 

 a prognostic of a change in the direction of the wind, which 

 will in the course of a few hours invariably spring up from 

 an opposite quarter. In such case it is highly probable (as 

 has been stated,) that a change has already taken place in the 

 direction of the upper strata of the air, although from theo- 

 retical considerations we might infer that the same result 

 would be produced if the wind were stationary above and 

 moving with a considerable velocity in a direction opposite 



