Tyndall, John, 1820-1893 · London : Longmans, Green · leaf 37
l, and both heand his friends were thus made acquainted with secretswhich were the reverse of amusing to one of the party. * It is recorded that a bell placed on an eminence in Heligoland failed,on account of its distance, to be heard in the town. A parabolic reflectorplaced behind the bell, so as… … ECHOES. 17 VMien a sufficient interval exists between a direct anda reflected sound, we hear the latter as an echo. Sound, like light, may be reflected several times insuccession, and as the reflected light under these circum-stances becomes gradually feebler to the eye, so the suc-cessive echoes…
Sound
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