W. B Taylor— Recent Researches in Sound. 99 



point on the coast without being felt more than a few miles in 

 the interior, the air continuously flowing in below and going 

 out above. Indeed in such cases a break in the lower clouds 

 reveals the fact of the existence above of a rapid current in the 

 opposite direction." (p. 92.) 



Professor Henry's attention had been directed to this point as 

 early as 1865, by discovering that a signal was audible against 

 the wind at the mast-head of a vessel, after ceasing to be audi- 

 ble on deck: Obs. [4]. "This remarkable fact at first sug- 

 gested 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 on the banks of Newfoundland in the 

 occupation of fishing : ' When the fishermen in the morning 

 hear the sound of the surf to leeward, or from a point toward 

 which the wind is blowing, they take this as an infidlible indi- 

 cation that in the course of frorn one to five hours the wind will 

 change to the opposite direction from which it is blowing at the 

 time.' The same statement was made to me by the intelligent 

 keeper of the fbg-sigual at Block Island. In these cases it 

 would appear that the wind had already changed direction 

 above, and was thus transmitting the sound in an opposite 

 direction to that of the wind at the surface of the earth." (Kep., 

 p. 92.) The full significance of this idea ho 

 ' esis of Professor i 



considered. This appeared 

 ved efl'e 

 ^ , I the direction of 



Professor Tyndall thus comments on the rival hypothesis of 

 Professor Henry: "In the higher regions of the atmosphere he 

 places an ideal wind, blowing in a direction opposed to the real 

 one, which always accompanies the latter, and which more than 

 neutralizes its action. In speculating thus he bases himself on 

 the reasoning of Professor Stokes, according to which a sound- 

 wave moving against the wind is tilted upward. The upper 

 and opposing wind is invented for the purpose of tilting again 

 the already lifted sound-wave downward." (Pref. to Sound, 

 pp. 19, 20.) 



The word " invented " is scarcely the most appropriate term 

 for an hypothesis derived from such patient research and care- 

 the case considered, the reversed 

 culation is rendered so probable bv 

 presented, it is proper to remark that this 

 condition is not at all essential to the refraction doctrine. The 

 hypothesis of Professor Stokes by no means assumes that -a 



