8^ Proceedings of the British Association. 



low roofs, having a good reflecting power, rough and interrupt- 

 ed walls, and a floor eitlier possessing very little resilience, such 

 as earthen floors do, or, if boarded, then much broken and in- 

 terrupted by irregular seating and matting, produced a building 

 best suited to the hearing of a speaker in many directions. He 

 exhibited a plan of his own chemical laboratory in Edinburgh, 

 in which these particulars were all exemplified ; and he declared 

 that a speaker, expressing himself in a tone very little above a 

 whisper, could be heard in the most remote parts of tliat room, 

 whether crowded or empty. The space not occupied by fur- 

 nace arrangements can accommodate about a thousand persons. 

 The power of the voice being proportioned to the intensity of 

 the sonorous impulse, the area through which it has to diffuse 

 itself, and the manner in which it is strengthened by reflection, 

 all superfluous space ought to be avoided as much as possible, 

 and the direct sound of the voice having been strengthened by 

 one reflection from the roof, it ought then to be entirely absorb- 

 ed, by being made to fall upon some non-reflecting surface. Dr 

 Reid then alluded to several public buildings in Dublin, where 

 practical illustrations of the views he had explained might be 

 obtained ; and, after a number of observations upon the form, 

 walls, roof, ornamenting, &c. of public buildings, and the manner 

 in which many might be much improved, alluded to the influence 

 of different strata of air in the same apartment, arising from im- 

 perfect ventilation, or from an equal distribution of heat, which 

 he shewed had considerable effect in some peculiar situations in 

 preventing the free and equal communication of sound. 



10. Mr Snow Harris on the nature of electrical attraction, ic'ith 

 experiments. The author is of opinion, that neither the theory 

 of one nor of two fluids explains all the phenomena of electrical 

 attraction and repulsion. He makes exceptions to the law of 

 the inverse square of the distance, as much depends upon the 

 state and circumstances of the bodies as evinced by delicate ex- 

 periments. He exhibited his apparatus for measuring the force 

 of attraction between electrified plates and spheres. Some ob- 

 servations made by Professor Powell and Mr Whewell shewed 

 that plates will attract nearly as the inverse distance of the mole- 

 cules attract in the inverse square. Mr S. Harris explained, 

 and remarked, that it was not his object to refute the theory of 



