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The true source of this echo, as we found by various experiments, is the stone-built, tiled hop-kiln in Gally-lane, which measures in front 40 feet, and from the ground to the eaves 12 feet. The true centrum phonicum, or just distance, is one particular spot in the Kings’-field, in the path to Nore-hill, on the very brink of the steep balk above the hollow cart way. In this case there is no choice of distance; but the path, by mere contingency, happens to be the lucky, the identical spot, because the ground rises or falls so immediately, if the speaker either retires or advances, that his mouth would at once be above or below the object.
We measured this polysyllabical echo with great exactness, and found the distance to fall very short of Dr. Plot's rule for distinct articulation : for the Doctor, in his history of Oxfordshire, allows 120 feet for the return of each syllable distinctly: hence this echo, which gives ten distinct syllables, ought to measure 400 yards, or 120 feet, to each syllable ; whereas our distance is only 258 yards, or near 75 feet, to each syllable. Thus our measure falls short of the Doctor's, as five to eight: but then it must be acknowledged that this candid philosopher was convinced afterwards, that some latitude must be admitted of in the distance of echoes according to time and place.
When experiments of this sort are making, it should always be remembered that weather and the time of day have a vast influence on an echo; for a dull, heavy, moist air deadens and clogs the sound; and hot sunshine renders the air thin and weak, and deprives it of all its springiness; and a ruffling wind quite defeats the whole. In a still, clear, dewy evening the air is most elastic; and perhaps the later the hour the more so. Echo has always been so amusing to the imagination, that the poets have personified her; and in their hands she has been the occasion of many a beautiful fiction. Nor need the gravest man be ashamed to appear taken with such a phænomenon, since it may become the subject of philosophical or mathematical inquiries.
One should have imagined that echoes, if not entertaining, must at least have been harmless and inoffensive; yet Virgil advances a strange notion, that they are injurious to bees. After enumerating some probable and reasonable annoyances, such as prudent owners would wish far removed from their bee-gardens, he adds
ant ubi concava pulsu Saxa sonant, vocisque offensa resultat imago." [There is a natural occurrence to be met with upon the highest part of our downs in hot summer days, which always amuses me much, without giving me any satisfaction with respect to the cause of it; and that is a loud audible humming as of bees in the air, though not one insect is to be seen. This sound is to be heard distinctly the whole common through, from the Money-dells, t to my avenue gate. *“ Nor place them where too deep a water flows,
Or where the yew, their poisonous neighbour, grows;
(DRYDEN's Virg. Georg. iv. 47-50.) † Bees high in the air, or clouds of minute insects in a similar position, it has been suggested, may cause this mysterious humming, which will be familiar to all who hare taken to the high grounds in a calm summer's day,-ED.
Any person would suppose that a large swarm of bees was in motion, and playing about over his head. This noise was heard last week, on June 28th. “ Resounds the living surface of the ground,
Nor undelightful is the ceaseless hum
To him who muses * * * * at noon."
Upward and downward, thwarting and convolvd,
The quivering nations sport.” This wild and fanciful assertion will hardly be admitted by the philosophers of these days; especially as they all now seem agreed that insects are not furnished with any organs of hearing at all.* But if it should be urged, that though they cannot hear yet perhaps they may feel the repercussion of sounds, I grant it is possible they may. Yet that these impressions are distasteful or hurtful, I deny, because bees, in good summers, thrive well in my outlet, where the echoes are very strong: for this village is another Anathoth, a place of responses or echoes. Besides, it does not appear from experiment that bees are in any way capable of being affected by sounds:t for I have often tried my own with a large speaking-trumpet held close to their hives, and with
* Brunelle's experiment set this strange conclusion at rest. He kept several males of the large grasshopper in a closet. A tap at the door of this closet at once intercepted their chirping, and produced silence. He also learned to imitate, and they immediately answered him. Other variations of the experiment quite satisfied him that the male and female heard and responded to each other.-ED.
† Did the author never hear of the practice bee-keepers have of beating on a gong, or its substitute a tea-tray, to induce hiving bees to settle? All who have witnessed this strange and interesting incident must admit that bees exhibit an acute sense of sound, not in the repercussive sense only, but to follow the sound. -ED.
such an exertion of voice as would have hailed a ship at the distance of a mile, and still these insects pursued their various employments undisturbed, and without showing the least insensibility or resentment.
Some time since its discovery this echo is become totally silent, though the object, or hop-kiln, remains: nor is there any mystery in this defect; for the field between is planted as an hop-garden, and the voice of the speaker is totally absorbed and lost among the poles and entangled foliage of the hops. And when the poles are removed in autumn the disappointment is the same; because a tall quick-set hedge, nurtured up for the purpose of shelter to the hop ground, interrupts the repercussion of the voice : so that till those obstructions are removed no more of its garrulity can be expected.
Should any gentleman of fortune think an echo in his park or outlet a pleasing incident, he might build one at little or no expense. For whenever he had occasion for a new barn, stable, dog-kennel, or the like structure, it would be only needful to erect this building on the gentle declivity of an hill, with a like rising opposite to it, at a few hundred yards distance; and perhaps success might be the easier ensured could some canal, lake, or stream, intervene. From a seat at the centrum phonicum he and his friends might amuse themselves sometimes of an evening with the prattle of this loquacious nymph; of whose complacency and decent reserve more may be said than can with truth of every individual of her sex; since she is “always ready with her vocal response, but never intrusive:”
quæ nec reticere loquenti, Nec prior ipsa loqui didicit resonabilis echo.”
The classic reader will, I trust, pardon the following lovely quotation, so finely describing echoes, and so poetically accounting for their causes :
“Quæ benè quom videas, rationem reddere possis
Tute tibi atque aliis, quo pacto per loca sola
(LUCRETIUS, Lib. iv l. 576.)
(CREEch's Translation.) SELBORNE, Feb. 12, 1778.