WHISPERING GALLERY. 283 



nearly a mile distant from a weir across a river. When 

 the air is pure and homogeneous, the rushing sound 

 of the water is reflected from the hollow surface 

 of the wall, and concentrated in a focus, the place of 

 which the ear can easily discover from the intensity of 

 the sound being there a maximum. A person not ac- 

 quainted with the locality conceives that the rushing 

 noise is on the other side of the wall. 



In Whispering Galleries, or places where the lowest 

 whispers are carried to distances at which the direct 

 sound is inaudible, the sound may be conveyed in two 

 ways, either by repeated reflections from a curved surface 

 in the direction of the sides of a polygon inscribed in a 

 circle, or where the whisperer is in the focus of one 

 reflecting surface, and the hearer in the focus of another 

 reflecting surface, which is placed so as to receive the 

 reflected sounds. The first of these ways is exemplified in 

 the whispering gallery of St. Paul's, and in the octagonal 

 gallery of Gloucester Cathedral, which conveys a whisper 

 seventy- five feet across the nave, and the second in the 

 baptistery of a church in Pisa, where the architect Giovanni 

 Pisano is said to have constructed the cupola on purpose. 

 The cupola has an elliptical form, and when one person 

 whispers in one focus, it is distinctly heard by the person 

 placed in the other focus, but not by those who are placed 

 between them. The sound first reflected passes across the 

 cupola, and enters the ears of the intermediate persons, but 

 it is too feeble to be heard till it has been condensed by a 

 second reflection to the other focus of ellipse. A naval 

 officer, who travelled through Sicily in the year 1824, 

 gives an account of a powerful whispering place in the 

 cathedral of Girgenti, where the slightest whisper is 

 carried with perfect distinctness through a distance of 

 250 feet, from the great western door to the cornice 

 behind the high altar. By an unfortunate coincidence 



