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 convey ance of reflected as well as direct sound. I believe 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." "It was in the church of Pont-Charenton, on the Seine,” replied Mr Seymour; "in which place that great philosopher discovered the inability of an echo to return the letter S ; for having pronounced the word Satan, the echo replied va-t-en-away; from which circumstance, the Parisians concluded that some guardian spirit prevented the walls of the sacred edifice from pronouncing the name of Satan.” "And will not an echo repeat the letter S ?" asked Louisa. "Not always," answered her father; "the hissing or sibilant noise of the letter, when at the commencement of a word, is generally lost, unless the echo be extremely perfect." Mr Seymour was here reminded of an echo on the Rhine, near the ruin of Rheinfels, to which is usually addressed the question-" Who is the Mayor of Oberwesel ?" the echo answers Esel,* -an Ass.. * The stand upon which the painter | its carrying, like the ass, the burthen rests his picture is termed an Esel, from on his back. "To be sure," said the vicar, "the latter syllables returned by the echo are those which retain possession of the ear. My young friends, no doubt, remember the facetious dialogue between Juvenis and Echo in the colloquy of Erasmus, in which a very humorous application is made of this circumstance." The party now set off on their excursion to the valley. Mr Seymour disposed them in such situations as were best calculated to display the powers of the echo, and to illustrate the several effects which he had endeavoured to explain. The vicar performed his experiment with dactyles and spondees, and was highly gratified to find that their results proved, in a most satisfactory manner, the correctness of his conjecture. The attention of Miss Villers was particularly directed to the effect of the voice of Mrs Seymour from the orchard gate, and which, she said, convinced her that the sound she had heard on the preceding evening must have arisen from the cause assigned to it. After the party had fairly tired themselves by their converse with the airy and unsubstantial being, they descended to the sandstone rocks, which Mr Seymour pointed out as the local habitation of the solitary spirit. These were duly examined by Louisa and Tom, and their operation as a reflecting screen was pointed out to them by their father. "I can now perfectly understand the possible deceptions to which an echo can give rise," said Miss Villers; "and I have no doubt that many sounds, to which credulity has given a supernatural origin, may thus receive a ready explanation." "Without doubt," repeated Mr Seymour; "and I will give you an example, which just at this moment occurs to me. The miners of Cornwall, a very superstitious race, entertain a notion that little spirits, or fairies, whom they call 'Piskeys,' are ever working in the richest parts of the mine, to which their prescience had directed them, and that when their pickaxes are heard, it may be taken for granted that some rich ore abounds in the neighbourhood. We may very safely accept the conclusion, while we reject the superstition: the explanation is simply this:—that cavities in the rock are geologically associated with an accumulation of ore; the sound, therefore, heard by the working miner is but the reverberation of his own pickaxe, from some contiguous cavity." The major was greatly interested by this discussion, and amused the party by relating the experience he had gained from echoes and vibrations during the progress of a siege: he said that he had himself heard in a "listening gallery," during a mining operation, the stroke of the pick; and that by the vibration of a pea placed upon a tightlybraced drum, he had discovered the subterraneous workmen at the distance of sixty feet. The party now returned to the geological temple: its singularlybeautiful pillars very naturally attracted the attention of Miss Villers, and she expressed a wish that Mr Seymour should describe the plan of their construction: for it was very evident, as she said, from the disposition of the specimens, that the arrangements had been directed with some view to geological illustration. Mr Seymour felt gratified by this request, and promised to comply with her wishes, as soon as he had finished the investigation of those laws by which the reflection of sound was governed. "Why, bless me !" exclaimed the vicar, "the revels of our airy companion are ended; and I maintain that nothing can be more appropriate than the consideration of the objects for which Miss Villers has expressed so much interest. In truth, the history of Echo is classically associated with that of geology: by diving into the recesses of the rock, we do but pursue her descent from air to earth; for you, no doubt, remember that, after she had been deprived of her loquacity by Juno, she became enamoured of Narcissus, pined away, and was transformed into stone." * “I cannot but admire the ingenuity with which you embellish every subject with classical decorations," replied Mr Seymour. "I was about," said he, "to explain to my young pupils the principle and construction of the Whispering Gallery in the dome of St Paul's; but it will, probably, be more convenient that I should postpone the consideration of this, and some other subjects in connexion with it, until after our return to the Lodge: I am not, however, disposed to pass over the fable of Echo and Narcissus, to which you have just alluded, without maintaining, in opposition to the critical disparagement of Addison, that it is one of the most beautiful myths of antiquity. Every stage of it appears to me to admit of an allegorical interpretation. Whether the poet was acquainted with the laws by which the reflection of sound and light is governed may certainly be questioned; but the fable undoubtedly shadows forth a remarkable example of poetic and retributive justice. Narcissus is represented as disdaining the plaintive appeal of Reflected Sound, and is sacrificed to the illusive charms of Reflected Light." The vicar expressed himself as highly gratified by so novel and ingenious an interpretation; and Mr Seymour then proceeded to view the details of the geological temple, and the design of the pillars that had so agreeably excited the curiosity of Miss Villers. * Ovid, Metamorph. iii. 358. CHAPTER XX. ON their return to the Lodge, Mr Seymour proceeded with the explanation of the Whispering Gallery in St Paul's Cathedral; and, in order to render intelligible the manner in which sound is concentrated, and thereby magnified, in that hollow hemisphere, he produced a diagram, of which the annexed cut is a copy. 66 M shows the situation of the mouth of the speaker, and E that of the ear of the hearer. Now, since sound radiates in all directions, a part of it will proceed directly from м to E, while other rays of it will proceed from м to u, and from м to z, &c.; but the ray that impinges upon u, will be reflected to E, while that which first touches z will be reflected to y, and from thence to E; and so of all intermediate rays, which are omitted in the figure, to avoid confusion. It is evident, therefore, that the sound at E will be much stronger than if it had proceeded immediately from м without the assistance of the dome; for, in that case, the rays at z and u would have proceeded in straight lines, and consequently could never have arrived at the point E." "I have understood that a similar effect was formerly witnessed in the stone recesses on Westminster Bridge," said the vicar. "That is the fact," replied Mr Seymour. "The recesses to which you allude were semi-domes; and if a person whispered in the focus of one of them, he was distinctly heard by another stationed in the focus of the opposite one. Two inanimate busts may be thus made to appear as if holding a conversation, by placing them in the foci of two large concave mirrors constructed of pasteboard, and arranged opposite to each other; when a whisper uttered to the one will seem to proceed from the other by the reflection of sound." Mr Seymour now removed a shell from a group of corallines, which decorated a part of the temple, and desired Tom to place it to his ear. "I hear a noise which appears to me to resemble that of the sea," cried Tom. "Ay," said the vicar, " and there is a popular belief that it is the murmur of the sea, which the shell actually sends forth, betraying, as it were, its marine origin.”* "And what produces the sound?" inquired Louisa. "The interior of the shell merely concentrates, and thus magnifies the sounds around us, so as to render them audible: a goblet applied to the ear, will be found to produce the same effect,” replied her father. "I suppose it is upon the same principle that the speaking-trumpet is made to convey sound to a distance," remarked Louisa. "Since sound radiates in all directions, it follows that, if such radiation be prevented by confining it in tubes, it may be carried to a great distance with very little diminution of its effect; and hence the use and application of those trumpets, or tin speaking-pipes, which are now commonly used for conveying intelligence from one part of a house to another. The trumpet used by deaf persons acts on the same principle; but as the voice enters the trumpet at the large instead of the small end of the instrument, it is not so much confined, nor is the sound so much increased." "I believe," said Mrs Seymour, "that the experiment exhibited some time since in London under the title of the Invisible Girl, and which excited such general curiosity, was discovered to depend upon an arrangement of this kind." The vicar observed, that it was found out by his late friend Dr Milner, the learned and scientific President of Queen's College, Cambridge. "I expected that you would allude to that exhibition," said Mr Seymour; "and as I was anxious to provide my young pupils with some new amusement, as a reward for their industry, I have directed Tom Plank to construct the necessary apparatus for exhibiting and explaining the deception." Upon inquiry, Mr Seymour found, as he had anticipated, that the necessary apparatus for the experiment of the "Invisible Girl" had been duly arranged, and that Tom Plank was in attendance to afford any assistance which might be farther required. We shall proceed to describe all the visible mechanism, as it appeared to the children on "Apply The polish'd lips to your attentive ear, And murmurs, as the ocean murmurs there.' |