Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER VI. Natural Ventilation. Rules respecting Ventilation. — Natural and Artificial Ventilation.— Ventilation through Window, Wall, Chimney, ana Ceiling. Most treatises on ventilation and heating have been founded on European facts and figures, and are hence unreliable for the American climate. And even in speaking of the States alone, it is difficult to give general methods which shall be applicable to the great diversities of climate included in its 25" of latitude, of which the only one feature in common is the inconstancy of the climate. New York, for instance, has been said to have the summer of Rome, and the winter of Copenhagen. Ventilation is constantly being produced by two natural agencies, viz., the diffusion of gases, and the movements caused by differences of temperature. Diffusion, by which the purer outside gases tend to mix with the impure internal air, is constamiy going on, tnougn the rate of diffusion is under ordinary circumstances slow and the amount of interchange thus effected is but small. Differences of temperature cause much more active movements of air, warm air floating to the top of cold air, as oil floats to the top of water. The air in a room is warmed by the inmates and by the stove, gas, or other source of artificial haat. Cold air tends to rush in from every opening, and, being heavier than warm air, falls toward the floor, producing a draught. The great problem of ventilation is to secure a sufficient interchange of air without causing draughts. The entrance of air at any temperature below 50 into a room whose temperature is 65 or even 70 is almost certain to be accompanied by draught; hence it is necessary to warm the entering air during many of the winter months. If a free entrance for pure air is not provided, the...