Quesnet has described another singular echo near Rouen, in the Memoirs of the Academy for 1664.
In the neighbourhood of Coblentz, on the banks of the Rhine, there is a very remarkable echo, which is described by Barthius, in his notes upon the Thebaid of Statius. He has heard it repeat words seventeen times) and it produces exactly the same effects as that at Genec fay, near Rouen.
At Locheneilan, a lake in Inverness-shire, and the property of J. P. Grant, Esq. of Rothiemurchus, there is a very fine echo. The wall of an old castle, in the middle of the lake, repeats several syllables with great distinctness; and when a pistol is fired, the sound is repeated about thirty times, from the numerous and lofty hills with which the lake is encircled.
In the neighbourhood of Edinburgh, in the King's Park, there is a place called the Echoing Rock. A per son standing in front of this, will hear repeated with great distinctness several syllables which he may utter. The sound is in this case reflected from a circular wall at no great distance, and the rock to which the property is ascribed merely happens to be near the centre of the circular wall.
In erecting the baptistery of the church of Pisa, the architect, Giovanni Pisano, disposed the concavity of the cupola in such a manner, that any noise from below is followed with a very loud and long double echo. The repetition, however, is not so distinct as that of Simon etta. Two persons whispering, and standing opposite to each other, with their faces near the wall, can con verse together without being overheard by the company between. This arises from the elliptical form of the
cupola, each person being placed in the focus of the ellipse.
In the cathedral church of Gloucester, there is a whis pering gallery above the eastern extremity of the choir, and which extends from one end of the church to the other. If two persons, placed at the distance of 25 toises, speak to one another in the lowest voice, it is distinctly heard. A similar effect is produced in the vestibule of the Observatory of Paris, and in the cupola of St Paul's in London. Mr Southwell informs us, that, in Italy, on the way to Naples, and two days journey from Rome, he saw in an inn, a square vault, where a whisper could easily be heard at the opposite corner ; but not at all on the side corner that was near to you. This property was common to each corner of the room. He saw another on the way from Paris to Lyons, in the porch of a com mon inn, which had a round vault. When any person held his mouth to the side of the wall, several persons could hear his whisper on the opposite side.
See Harris's Lexicon Technicum, Art. Eeno ; Birch's Hist. of the Royal Society, vol. i. p. 1.37; Addison's Travels, Edit. 1718, p. 32; Keysler's Travels, vol. i. p. 428, 490 ; Southwell, Phil. Trans. 1746, vol. xliv. No. 480. p. 219 ; Guynet, Menz. Acad. Par. 1770, Hist. 23 ; Quesnet, Mem. Acad. Par. 1666, tom. ii. p. 87; Abbe Gallois, Menz. Acad. Par. tom. x. p. 127; Actis, Mem. Turin, 1788, vol. iv. App. 43. (9r)