OS TUT. CONSTRUCTION OF THEATRES. }$S 



topper frames, turning upon centres so as to open at plea- 

 sure like Venetian window-blinds ; and by this means to 

 contract, at will, the opening of the ceiling, and to con» 

 duct the voice of the performers towards the audience. The A gentle cxxv 



current of air, so as it does not amount to wind, should r f nt ?!i IP 

 ' * „ should flo\r 



flow from the stage to the audience. By experiments tried from the 

 upon sound by Sir Thomas Morland and some other mem- sta S e * 

 bers of the Royal Society, it appeared, that the propaga- 

 tion of sound was prodigiously obstructed by the assistance 

 or opposition of a slight current of air. We are told by Sound in- 

 Vitruvius, and Lipsius, that the sound of the actor's voice brazen vessels 

 was increased in a surprising manner by brazen vessels umlerthe 

 placed under the seats of the audience. 



No satisfactory account remains of the manner in which, 

 this desirable effect was produced. It would not however 

 be difficult to try experiments on this subject in any one of 

 our theatres when it is vacant. 



About 40 years ago I happened to go with a friend into Sound m- 

 a large cockpit at an inn at Towcester, My friend, who creased by 

 was at the opposite side of the pit, appeared to me to behind the'au- 

 speak with a yoice uncommonly loud and sonorous. Upon, ditor*. 

 toy inquiring why he spoke in that manner, he said, that 

 he had not raised his voice above its ordinary pitch. Upon 

 looking about I perceived a large earthen jar behind me, 

 which proved the cause of this increase of sound : for upon 

 repeated trials the voice of my friend sounded as usual when 

 1 stood in any other part of the cockpit, but that in which 

 the vase was placed. To the best of my recollection the 

 jar was about rive feet high, and twenty inches in diameter. 

 1 remember well, that it rung clearly, but slowly, when 

 struck wi{h the knuckle. By what means, and by what 

 materials, the pulses of sound may be best returned forth© 

 purposes we have in view, is a subject for the joint efforts 

 of mathematics aud experiment. 



Among other expedients pannelling the backs of the Expedient 

 boxes with thin elastic plates of brass might be tried. e 



A saving and advantage would certainly arise in all cases 

 from using iron, or copper, instead of wood;they would not re- 

 quire renewal for many years, and they would be apreservative 



against 



