388 WRITINGS OF JOSEPH HENRY. 



[1874 



which was probably due to increase of the force of the wind ; 

 the trumpet was lost at 3| miles. 



In all these observations, owing to the unfavorable con- 

 ditions of the locality, and the direction of the wind, we were 

 unable to obtain any satisfactory observations on sound 

 moving with the wind. In all cases the results were obtained 

 from sounds moving nearly against the wind, or at right 

 angles to it. From the results of the whole it appears that 

 the sound was heard farther with a light opposing wind 

 than with a stronger one, and that it was heard farthest of all 

 at right angles to the wind. From this latter fact however 

 it should not be inferred that in this case sound could be 

 heard farther at right angles to the wind than with the wind, 

 but that in this direction the effect of the wind was neutra- 

 lized. The results also exhibited, in a striking manner, 

 the divergency of sound from the axis of the trumpet, the 

 trumpet being heard in the line of its axis in front at 6 miles 

 and behind at 3 miles, the wind being nearly the same in 

 both cases. 



All the observations were repeated on land with the arti- 

 ficial ear as far as the unfavorable condition of the surface 

 would permit. Although the limit, as to distance, at which 

 the sand might be moved was not in most cases observed, 

 yet the relative degree of agitation at a given distance estab- 

 lished clearly which was the most powerful instrument, the 

 result giving precisely the same order of penetration of the 

 different instruments as determined by direct audition. 



During this series of investigations an interesting fact 

 was discovered, namely, a sound moving against the wind, 

 inaudible to the ear on the deck of the schooner, was heard 

 by ascending to the mast-head. This remarkable fact at first 

 suggested the idea that sound was more readily conveyed 

 by the upper current of air than the lower, and this appeared 

 to be in accordance with the following statement of Captain 

 Keeney, who is commander of one of the light-house vessels, 

 and has been for a long time engaged on the banks of New- 

 foundland in the occupation of fishing: "When the fisher- 

 men in the morning hearths sound of the surf to the leeward, 



