56 Scientific Proceedings, Royal Dublin Society. 



was not found practicable to distinguish all the elements which 

 theory seems to indicate, but of the marked improvement effected 

 by introducing the canopy there can be no doubt. 



This concluded the first part of the inquiry. The second was 

 directed towards ascertaining whether it is possible to construct a 

 room without echo, or to alter an existing room in such a way as 

 will free it from echo. The experiment I proposed to make was to 

 hang paper draperies on the walls and from the ceiling ; but before I 

 incurred the considerable trouble and expense of doing this I acci- 

 dentally found that one of the large apartments of the Exhibition 

 Palace, in Earlsfort-terraee, had its walls papered over a lining of 

 canvas, the canvas being a short distance (from One-eighth to a 

 quarter of an inch) in front of the framework over which it was 

 stretched. These are precisely the conditions that I had desired ; 

 and, very fortunately, the ceiling of this room is so nearly covered 

 by skylights that there is but little echo from it. On trying the 

 experiment in this room, with the floor occupied by an audience, 

 I found no appreciable echo that could be referred to the walls. 

 There was indeed a very short echo, very unlike the prolonged 

 echo of an ordinary room of the same shape and size, sounding like 

 the letter R very roughly pronounced, with a faint burst, which 

 lasted not, I think, more than the eighth or tenth of a second. 

 This I. believe to have been due to the partitions which separate 

 the numerous skylights of which I have spoken. 



■ From this experiment I believe it may be safely inferred, that 

 a concert hall or room for public oratory may be effectually freed 

 from echo by the extremely simple expedient of lining its walls 

 and ceiling with canvas, kept at a slight distance away from the 

 walls. The ceiling must be included in this treatment, if it" is to 

 be effectual, as a large part of the echo usually comes from it. The 

 canvas may be papered, or distempered, or painted, so that there 

 need not even be any change in the room visible to the eye. 



