“In a moderate way of speaking, about three and a half syllables are pronounced in one second, or seven syllables in two seconds; when an echo, therefore, repeats seven syllables, we may infer that the reflecting object is 1142 feet distant.”
“But, my dear Mr. Seymour, this must surely depend upon the nature of the syllables,” said the vicar. “Pray excuse the interruption; but you will admit that there must exist a great difference between the echo of dactyles and spondees. Suppose an echo should be able to return ten syllables; thus--
‘Tityre, tu patulæ recubans--’
I will be bound for it, that if you were to try its powers in slow heavy spondees, as monstrum horrendum, a return of not more than four or five syllables could be observed.”
“I will not dispute that point,” said Mr. Seymour.
Louisa here remarked that she had often heard of some very extraordinary echoes in different parts of the world, to which her father had not alluded; she mentioned, for instance, those which are said to repeat the same sound several times in succession.
“From the explanation which I have already given of the nature of echoes,” said Mr. Seymour, “it will be easily conceived that a vast variety of effects may be produced by varying the form, the shape, the distance, and the number of reflecting surfaces: and hence we hear of various surprising echoes in different places. It is not difficult, for instance, to understand the nature of compound, or tautological echoes; in which case the expression of one ha will appear like a laughter. Addison mentions an extraordinary instance of this kind near Milan, which will return the sound of a pistol fifty-six times.”
“I have understood that the echoes on the lakes of Killarney are of this multiplied description,” said the vicar.
“They are particularly calculated to produce reflections of sound, from the height of the mountains, and the expanse of water,” replied Mr. Seymour, “which latter circumstance always assists the conveyance of reflected, as well as direct sound. I believe that there is a certain spot on the shore of Ross island, where the sound of a bugle produces an echo which far exceeds any other to be met with amongst the lakes; the first echo is returned from the castle, the second from the ruined church of Aghadoe, the third from Mangerton, and afterwards innumerable reverberations are distinguished, which, like the faded brilliancy of an extremely multiplied reflection, are lost by distance and repetition.”
“There is an admirable echo,” said the vicar, “behind my old college at Cambridge; and often have I, while walking on the road to Chesterton, on a calm evening, distinctly heard twelve repetitions of the voice. Lord Bacon, if I remember correctly, mentions an instance of sixteen, in some ruined church near Paris.”