the case 



REMARKABLE ECHOES. 281 



the case in an amphitheatre of mountains, or during a 

 thunder-storm, where there are several strata or masses 

 of clouds ; or if there are two parallel or inclined surfaces 

 between which the sound can be repeatedly reflected, or 

 if the surface is curved so that the sound reflected from 

 one part falls upon another part, like the sides of a 

 polygon inscribed in a circle in all these cases there 

 will be numerous echoes, which produce a very singular 

 effect. Nothing can be more grand and sublime than the 

 primary and secondary echoes of a piece of ordnance 

 discharged in an amphitheatre of precipitous mountains. 

 The direct or primary echoes from each reflecting surface 

 reach the ear in succession, according to their different 

 distances, and these are either blended with or succeeded 

 by the secondary echoes which terminate in a prolonged 

 growl ending in absolute silence. Of the same character 

 are the reverberated claps of a thunder-bolt reflected from 

 the surrounding clouds, and dying away in the distance. 

 The echo which is produced by parallel walls is finely 

 illustrated at the Marquis of Sinaonetta's villa near Milan, 

 which has been described by Addison and Keysler, and 

 which we believe is that described by Mr. Southwell in 

 the Philosophical Transactions for 1746. Perpendicular 

 to the main body of this villa there extend two parallel 

 wings about fifty-eight paces distant from each other, and 

 the surfaces of which are unbroken cither with doors or 

 windows. The sound of the human voice, or rather a 

 word quickly pronounced, is repeated above forty times, 

 and the report of a pistol from fifty-six to sixty times. 

 The repetitions, however, follow in such rapid succession 

 that it is difficult to reckon "them, unless early in the 

 morning before the equal temperature of the atmosphere 

 is disturbed, or in a calm still evening. The echoes 

 appear to be best heard from a window in the main 

 building between the two projecting walls, from which the 



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