DISCOURSE OF W. B. TAYLOR. 355 



and under great variety of both topographical and meteorological 

 conditions, untiringly prosecuted by numberless sea trips of 10, 

 15, and even 20 miles in single stretches, in calm, in sunshine, in 

 storm, with every variety of disregarded exposure, form altogether 

 a labor and a research, quite unequalled and unapproached by any 

 similar ones on record. As a result of so great earnestness and 

 thoroughness in the conduct of an enterprise of so great difficulty, 

 Henry has advanced and enriched our knowledge by contribu- 

 tions to the science of acoustics, unquestionably the most important 

 and valuable of the century. By persistent cross-examination of 

 the bewildering anomalies of sound propagation under wide diver- 

 sities of locality and condition, he has succeeded in evolving order 

 out of apparent chaos, in reclaiming a new district, now subjected 

 to the orderly reign of recognized law, and in raising the plausi- 

 ble but long neglected hypothesis of Stokes into the domain of a 

 verified and fully established theory. Only on the subject of the 

 ocean echo had he failed to reach a solution which entirely satisfied 

 his judgment;* and at the ripe age of four-score years he had 

 mapped out a further extension of his laborious search after truth, 

 when his untiring and beneficent purposes were cut short by death. 

 With these great labors (a full demand upon the energies of 

 youthful vigor) fittingly closed the life of one whose long career 

 had been dedicated to the service of his race, no less by the unre- 

 corded incitations and encouragements of others to the prosecution 

 of original research, than by his own direct and earnest efforts on 

 all occasions to extend the boundaries of our knowledge. Nor is 

 it permitted us to indulge in vain regrets that thirty years of such 

 a life were seemingly so much withdrawn from his own chosen 



*"The question, therefore, remains to be answered: what is the cause of the 

 aerial echo? As I have stated, it must in some way be connected with the hori- 

 zon. The only explanation which suggests itself to me at present is, that the 

 spread of the sound which fills the whole atmosphere from the zenith to the 

 horizon with sound-waves, may continue their curvilinear direction until they 

 strike the surface of the water at such an angle and direction as to be reflected 

 back to the ear of the observer. In this case the echo would be heard from a 

 perfectly flat surface of water, and as different sound-rays would reach the water 

 at different distances and from different azimuths, they would produce the pro- 

 longed character of the echo and its angular extent along the horizon. While 

 we do not advance this hypothesis as a final solution of the question, we shall 

 provisionally adopt it as a means of suggesting further experiments in regard to 

 this perplexing question at another season." '(Report of L. H. Board, 1877, p. 70.) 



