Gilbert White was intrigued by echoes and in A Natural History of Selborne considered the means whereby 'any gentleman of fortune' could create the conditions for listening to echoes in his park by erecting an appropriate structure 'on the gentle declivity of an hill, with a like rising opposite to it... 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.' The text here is from Letter XXXVIII, February 12th, 1778 (the Latin at the end means ‘answering echo, who has yet to learn / To keep her peace when spoken to, or speak the first in turn’):
In a district so diversified as this, so full of hollow vales, and hanging woods, it is no wonder that echoes should abound. Many we have discovered that return the cry of a pack of dogs, the notes of a hunting-horn, a tunable ring of bells, or the melody of birds, very agreeably: but we were still at a loss for a polysyllabical, articulate echo, till a young gentleman, who had parted from his company in a summer evening walk, and was calling after them, stumbled upon a very curious one in a spot where it might least be expected. At first he was much surprised, and could not be persuaded but that he was mocked by some boy; but, repeating his trials in several languages, and finding his respondent to be a very adroit polyglot, he then discerned the deception [...]
All echoes have some one place to which they are returned stronger and more distinct than to any other; and that is always the place that lies at right angles with the object of repercussion, and is not too near, nor too far off. Buildings, or naked rocks, re-echo much more articulately than hanging wood or vales; because in the latter the voice is as it were entangled, and embarrassed in the covert, and weakened in the rebound.
The true object of this echo, as we found by various experiments, is the stone-built, tiled hop-kiln in Galleylane, 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 King's-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 [....]
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… quae nec reticere loquenti, Nec prior ipsa loqui didicit resonabilis echo.