WHISPERING GALLERY. 225 



lowest whispers are carried to distances at which 

 the direct sound is inaudible, the sound may be 

 conveyed in two ways, either by repeated re- 

 flexions 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 re- 

 flecting 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 Glou- 

 cester 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 

 reflexion 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 distinct- 

 ness through a distance of two hundred and fifty 

 feet, from the great western door to the cornice 

 behind the high altar. By an unfortunate coin- 

 cidence, the focus of one of the reflecting surfaces 

 was chosen for the place of the confessional ; and 

 when this was accidentally discovered, the lovers 

 of secrets resorted to the other* focus, and thus 

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