with Reference to Sound. 27 
masses, through registers, not unfrequently placed along the cen- 
tral aisle of the room, and, not readily mixing with the surround- 
ing atmosphere, rises in unbroken columns to the ceiling, whence 
it is at length diffused. By these shafts of heated air the sono- 
rous vibrations are refracted, confused and obscured, the philo- 
sophical explanation of which we have already shown in the 
analogous effect upon light passing through strata of different 
densities and natures. he testimony of Dr. Reid in this par- 
ticular is important. In his evidence before the Parliamentary 
Committee, he says: 
“Another interruption to sound is the great body of air rising from 
the middle of the House, when the heating apparatus is in action; 
from this cause members cannot hear on the opposite sides, or the 
speaker persons at the bar.” 
One of the Committee also, when Reid mentioned this circum- 
stance, stated that he had often noticed he could not hear a mem- 
er Opposite him distinctly, at particular times, unless he shifted 
his seat along the bench; and on examining the place referred to, 
it was found that he had moved to a position where the hot cur- 
rent no longer passed between him and the member speaking.* 
If not found practicable to give the air on its admittance the uni- 
versal diffusion suggested in the plans just quoted, it can be made 
to enter after being previously tempered, beneath the benches all 
over the house, or through a continuous succession of apertures 
pierced in the floor, along the borders of the room, where an aisle 
might be left for that purpose. Better still, perhaps, a channel 
might be left in the walls close to the floor, and extending com- 
pletely around the room, masked by perforated panel work, through 
which the attempered air would gradually flow into the apart- 
ment. It would be easy, in this way, to obtain an aggregate area 
of inlet apertures equal to that proposed in Mr. Sylvester’s plan. 
Not less important is it, also, to secure a gentle and equable 
movement of the entire mass of air through the apartment. With 
properly graduated inlets and outlets, arranged in the manner just 
described, together with the provision of a constant, controllable 
motive power (which is all important, ) this result would natural- 
ly follow, were it not for other and foreign elements of disturb- 
ance.t Among the most serious of these is a predominance of 
* In the old Tremont Temple at Boston, the air was introduced in this way, as is 
still the case at the Melodeon in that city and at the Musical Fund Hall in P - 
say eae half a foot d, or about a mile per 
€ house would be a per second, or about one A 
= ur. At this rate, he says, a volume of air scarcely moves the most sensitive 
* 
