Notices of the proceedings at the meetings of the members of the Royal Institution of Great Britain with abstracts of the discourses . A Fig. 3.—To Illustrate a Simple Mechanical Application ofthe Principle of Reciprocity. my own observations, made in St. Pauls Cathedral, I think thatAirys explanation is not the true one ; for it is not necessary, inorder to observe the effect, that the whisperer and the listener shouldoccupy particular positions in the gallery. Any positions will doequally well. Again, whispering is heard more distinctly thanordinary conversation, especially if the whisperers
Notices of the proceedings at the meetings of the members of the Royal Institution of Great Britain with abstracts of the discourses . A Fig. 3.—To Illustrate a Simple Mechanical Application ofthe Principle of Reciprocity. my own observations, made in St. Pauls Cathedral, I think thatAirys explanation is not the true one ; for it is not necessary, inorder to observe the effect, that the whisperer and the listener shouldoccupy particular positions in the gallery. Any positions will doequally well. Again, whispering is heard more distinctly thanordinary conversation, especially if the whisperers face is directed. Fig. 4.—Model Illustrating the Peculiarities of aWhispering Gallery. along the gallery towards the listener. It is known that a whisperhas less tendency to spread than the full-spoken voice; thus awhisper, heard easily in front of the whisperer, is inaudible behindthat persons head. These considerations led me to form a fairlysatisfactory theory of the whispering gallery, nearly twenty-fiveyears ago.* The phenomenon may be illustrated experimentally * 1 Theory of Sound, § 287. 434 Lord Bayleigh on Shadows. [Jan. 15, by the small scale arrangement represented diagrammatically inFig. 4. A strip of zinc, about 2 feet wide and 12 feet long, isbent into the form of a semicircle ; this forms the model of thewhispering gallery. The bird-call B is adjusted so that it throwsthe sound tangentially against the inner surface of the zinc: itthus takes the place of the whisperer. The sensitive flame F takesthe place of the listener. A flame is always more sensitive to soundreaching it in one dir
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Keywords: ., bookauthorroyalins, bookcentury1800, bookdecade1850, bookyear1851
