98 W. B. Taylor — Recent Researches i 



found whether or not the sound was all the 

 his head. On the worst day an ; 

 extended the range nearly one qui 

 p. 76.) 



The instructive result, brought into view by the foregoing 

 summaries, is that the differences noticed are essentially those 

 of interpretation, and not to any important extent, of observation : 

 an illustration if any were needed, of the high and rare order of 

 imaginative insight requisite to the successful investigation of 

 the more recondite operations of natural law. The differing 

 actions of acoustic reflection and acoustic refraction suggested by 

 the ingenious hypotheses of Humboldt and of Stokes, and es- 

 poused respectively by Tyndall and Henry, are probably both 

 operative but their relative importance has yet to be established. 

 It is certain, as already indicated, that some of the phenomena 

 observed lie quite beyond the reach of the acoustic cloud 

 hypothesis. 



A particularly interesting case which is claimed with equal 

 confidence for either theory, is the remarkable observation of 

 General Duane, that at Portland, Maine, the steam whistle on 

 Cape Elizabeth, nine miles distant, " can always be distinctly 

 heard " with " the wind blowing a gale directly toward the 

 whistle" or against the sound. (L. H. Rep., p. 100.) At Port- 

 land Head, about midway between this fog-whistle and the 

 point of observation is another signal, — a Daboll trumpet. 

 While both these signals are better heard with an adverse 

 wind ("a heavy northeast snow storm") than at other times, 

 yet " as the wind increases in force, the sound of the nearer 

 instrument — the trumpet — diminishes, but the whistle becomes 

 more distincC (Rep., p. 92.) The abnormal influence of the 

 wind in reversing the order of these two signals is not the least 

 surprising feature of the general phenomenon. 



Professor Tyndall believes that this curious observation only 

 " proves the snow -laden air from the northeast to be a highly 

 homogeneous medium ;" (Sound, Preface, p. 19,) the 



ing air at other times being acoustically less transparent. 



Professor Henry supposes "that during the continuance of 

 the storm, while the wind was blowing from the northeast at 



the surface, there was a current of equal or greater intensity 

 blowing in an opposite direction above, by which the sound 

 was carried in direct opposition to the direction of the surface 

 current;" (Rep., p. 92)— somewhat in the nature of a vertical 

 cyclone. He adds : "The existence of such an upper current is 

 in accordance with the hypothesis of the character of a north- 

 east sto?-m, which sometimes rages for several days at a given 



