THE CONTROVERSY ON ACOUSTICAL RESEARCH. 481 



raents of fog-signaling as practised in tlie United States. On the 

 contrary, he acknowledges that in the choice of fog-signals for Brit- 

 ish use his " strongest recommendation applies to an instrument for 

 which we are indebted to the United States." He will remember, 

 moreover, that while he was sojourning in the United States he 

 souglit and obtained opportunities from Prof. Henry to observe the 

 operation of the steam-siren in the lighthouse at Sandy Hook. At 

 that time, if not before, he was made acquainted with the progress 

 not only of American science but also of American art under this 

 head. And in view of the fact that, as the " scientific adviser " of 

 the Elder Brethren of the Trinity House, he has counseled them to 

 discard their English horns and whistles and to substitute for them 

 the steam-sirens which have been, for several years, in the use of our 

 American lighthouses, it would seem that the second branch of the 

 claim advanced by the board at Washington stands in as little need 

 as the first of any additional reenforcement at our hands. Bacon re- 

 joiced in the fact that his philosophy was a philosophy which brought 

 forth fruit in the service of man. The progress of American science 

 in this department has been constantly bearing fresh fruit in the 

 interests of commerce and for the relief of the mariner. DaboU's 

 trumpet, an American invention, came to supersede the use of gongs, 

 and bells, and horns, and guns. To-day the steam-siren, an instru- 

 ment devised and perfected under the direction of the United States 

 Lighthouse Board, is acknowledged to be without a rival as an effi- 

 cient foor-signal. 



It is no part of our present purpose to institute a critical inquiry 

 into the conflicting views of Prof. Henry and of Prof, Tyndall with 

 regard to the hypotheses respectively espoused by each for the ex- 

 planation of the phenomena of sound in its passage through wide 

 tracts of air. Prof. Henry believes that the direction and the rate of 

 wind-currents are important elements in the problems presented by 

 the phenomena in question. Prof. Tyndall admits that " the well- 

 known eflect of the wind is exceedingly difficult to explain," but he 

 insists on making up the fagot of his scientific opinions on the subject 

 at once and foi'ever without taking the " viewless winds " into his 

 apcount. He finds a sufficient explanation of all the abnormal phe- 

 nomena in the assumption of ideal clouds of vapor mingling with the 

 atmosphere so as to disturb its homogeneity, and thereby to quench 

 the body of sound. There is nothing in the working hypothesis of 

 Prof. Henry which excludes any truth there may be in the working 

 hypothesis of Prof. Tyndall. But, in the present provisional state of 

 his inquiries on the subject, the former is disposed to question the 

 sufficiency of the explanation adduced by the latter as an efficient 

 cause of all the phenomena in question. With the modesty and re- 

 serve of the true physical philosopher, in the present unfinished state 

 of scientific inquiry. Prof. Henry waits for the wider knowledge which 



VOL. VIII. 31 



