212 ANNUAL OF SCIENTIFIC DISCOVERY. 



next essentials to perfect and distinct hearing are a tranquil atmosphere 

 and the absence of extraneous sounds. I consider them together, as we 

 shall find that the precautions essential to obtain the one will also secure 

 the other. Windows, in cold weather, separating the warm air within 

 from the cold air without, serve as refrigerators, cooling the air in contact 

 with the glass. The air, thus rendered heavier, immediately falls, and a 

 descending sheet of cold air is produced, which, on reaching the floor, 

 spreads over it in a cold stratum, and, to persons of sensitive nerves or 

 feeble health, causes great inconvenience, being felt as a draught upon the 

 feet and legs. And many an unfortunate page has been blamed for leav- 

 ing open a door, when the draught really has been caused by this air cooled 

 by the closed glass of an adjacent window. The circulation thus produced 

 of air of different densities is unfavorable to distinctness of hearing. As 

 the ascending hot air along a stove-pipe, or heated wall, causes irregular 

 refraction of light, and produces a tremulous appearance in all objects 

 viewed through it, so sound, irregularly refracted, becomes less clear and 

 distinct. If we exclude external windows, and light the room only from 

 the roof, we get rid of this fruitful source of discomfort and indistinctness ; 

 at the same time we obtain a pleasanter light, ample for all useful pur- 

 poses, as is proved by its adoption in all the best constructed picture gal- 

 leries. We also exclude the sounds of the exterior, which, saturating the 

 air, as it were, distract the attention, and even overpower the voice we 

 wish to hear, as the diffused light of day causes the stars to disappear. 

 Open windows for hearing will be worse than closed ones ; they not only 

 let irregular, disturbing currents of air in, but they let the voice out act- 

 ing like black spaces in the wall of a room, which do not return the light 

 which falls upon them. The common mode of warming and ventilating 

 public rooms is fatal to perfection of hearing. One or several columns of 

 intensely heated air are introduced through holes in the floor. Being 

 much warmer than the air of the apartment, they immediately rise to the 

 ceiling. If the exit- apertures for foul air are above, this fresh and heated 

 air alone escapes, having done nothing for the apartment except to cause 

 whirls and currents, such as we see in a column of smoke passing from a 

 chimney on a calm day. The irregular refraction of sound through these 

 currents of unequal density tends greatly to produce confusion. If the 

 exits for foul air a're below, the hot air accumulates at the top of the room, 

 and gradually displacing the cooler air, forces it out through these passages. 

 Professor Reid relates that he has found the air near the ceiling of a room 

 at the boiling temperature, while those on the floor were complaining of 

 cold. Her,e we have strata of different densities and unequal refractive 

 power, and hence confusion of sound. As the warm air must ascend to 

 the top of the room, I propose to letit do so in a large trunk outside of the 

 apartment, pass into a space above the ceiling, and thence, by numerous 

 holes, find its way, as through a sieve, into the room. By a steam-driven 

 fan, or other mechanical means, we can pump air, in any desired quantity, 

 into any spot to which we choose to direct it. I would drive ail the air 



