348 On the Construction of Buildings 
Art. XXXIX.—A Consideration of some of the Phenomena 
— and Laws of Sound, and their application in the Construction 
of Buildings designed especially for Musical Effect ; by J. B. 
Uruam, M.D., Boston. 
(Continued from p. 226.) 
We have treated of reflection and echo, in their relation to our 
subject, in a preceding number of this Journal. Intimately con- 
nected with, and yet distinct in some points from these attributes 
of sound, is reverberation. By it we understand that prolonga- 
tion of the sound in buildings, as if it were rolled about Jong 
after the original impulse and its ordinary reflections have ceased. 
This seems to us to consist of the residuary sound, or that por 
‘tion of the sonorous wave which is neither absorbed nor reflected, 
but which, adhering to the walls of a room, is rolled along theit 
surface till it gradually diesaway. The action of light imping- 
ing against a wall, under certain conditions, will, perhaps, aid us 
to understand this. When a ray of light is incident on the sur 
ce of an, transparent, uncrystallized medium, a portion of it's 
reflected, another portion of it is absorbed, and the remaining part 
is dispersed in all directions, and serves to render the surlace 
‘visi 
Just so it would appear to he in the case of seund impinging 
against any plane surface. From this hypothesis we should ine 
er that rounded corners and arched ceilings would facilitate the 
progress and keep up the prolongation of this residuary portion. 
Such conditions we find are actually favorable to the greatest 
amount of reverberation; and what is stronger proof of the truth 
of onr position, it takes place, oftentimes, in an apartment 100 
small for the injurious effect of direct reflection. — A striking case 
in point is found in the arched recitation rooms of Girard College 
in Philadelphia. These rooms, eight in number, are fifty feet 
square in the clear, and twenty-five feet high, with solid walls, 
smoothly finished, and an arched ceiling extending over each ID 
the form of adome. We visited these rooms in 1846, while the 
college was in process of construction, and then ventured the 
iction that they could never be made to serve the purpé i 
t which they were intended, unless altered from their origin 
opted to remedy the difficulty. In their original 0 se 
State, the prolongation of the sound in these rooms contin 
uly SIX seconds.* . 
fully 
— 
_ * It is but justice to state here that the ¢ es of this mode of constrny 
tion were fully appreciated by the architect, Mr. Walter. In his final report, spe 
