We have just come from one of our city churches, where we have had a striking example of this result. The church in question will _accommodate_ (?) about two thousand people. Twenty-five hundred may be crowded into it. At the commencement of the sermon, the preacher’s voice was distinctly audible at points fifty or sixty feet from the pulpit, in spite of reflections of sound--_air pulses_--from galleries, wooden columns, and the arched ceiling and side-walls, of lath and plaster. Before it was ended, the exhalations of the breathing crowd had so filled the lower half of the “_auditorium_” that only vowel sounds could be distinguished; and the _peroration_ seemed to consist of spasmodic utterances--scarcely sounds--of _a_, _e_, _i_, _o_, _u_. _W_ and _y_ had lost their affinity to vowels, and the rest of the alphabet were no longer _consonants_, for they were not heard at all.
The acoustic and sanitary problems are here identical--to find a method of preventing an accumulation of foul and inelastic vapors around the breathing and listening congregation, and to give, instead, wholesome air to their lungs, while enabling their ears to hear. And since these poisonous and inelastic gases are specifically heavier than atmospheric air, and must fall to the floor by their own weight, the problem is reduced to providing a practicable way for their escape, and guarding it against counter-currents which might obstruct the passage.
The introduction of warm air through openings in or near the floor will not readily produce uniformity of temperature within a room. The simplest experiment in proof of this is constantly made by multitudes of people, who, in crowded assemblies, find their heads surrounded by warm and moist vapors, reeking with offensive odors, while their feet are chilled, though near the “hot-air register.”
A library, whose walls were 12 feet high, and whose floor--18 by 15--contained 270 square feet, was constantly warmed by a “Latrobe heater,” placed in the chimney at one end of the room. The pot holding the coal was raised one foot above the level of the floor, which was covered by a woollen carpet. Immediately under the library was a kitchen, whose temperature was kept at about 72° F. Three thermometers were placed thus: No. 1, standing on the carpet near the centre of the library floor; No. 2, three feet, and No. 3, six feet, above it. At the expiration of half an hour, No. 1 indicated 62°; No. 2, 66°; and No. 3, 72°. Numbers 1 and 3 were then placed side by side with No. 2, three feet above the floor. At the expiration of fifteen minutes, all three indicated the same temperature of 66°. The low temperature of the inferior stratum of air was certainly not due to that of the room beneath it, for that was above 70°. It was only the heavier, colder air of the room itself, and of adjacent apartments warmed in the same way, slightly affected by contact with the stratum of warmer air above it.