2. In the winter, when our schoolrooms, churches, public halls, etc., are heated artificially, ventilation is comparatively easy if properly arranged. [Footnote: For the escape of bad air, Dr. Bell suggests that an efficient foul-air shaft may be fitted to the commonest of stoves by simply inclosing the stovepipe in a jacket--that is, in a pipe two or three inches greater in diameter. This should be braced round the stovepipe and left open at the end next the stove. At its entrance into the chimney, a perforated collar should separate it from the stovepipe.] The required difference of temperature is kept up with little difficulty. The fresh air admitted to the room should then be heated [Footnote: Ventilation is change of air, and, unless scientifically arranged, and especially unless the incoming volume of air be warmed in cold weather, such change of atmosphere means cold currents, with their attendant train of catarrhs, bronchitis, neuralgia, rheumatism, and all the evils that spring from these diseases. The raw, damp, frosty air of our ever-changing winter temperature ought not to have uncontrolled and constant ingress to our dwellings. Air out of doors is suited to out of door habits. It is healthy and bracing when the body is coated and wrapped, and prepared to meet it, and when exercise can be taken to keep up the circulation; but to live under cover is to live artificially, and such essential conditions must be observed as suit an abnormal state. All the evils attaching to ventilation, as it is generally effected, spring from the neglect of this consistency.--_Westminster Review_.] either by a furnace, or by passing over a stove, or through a coil of steam pipes. This cold air should always be taken directly from out of doors, and not from a cellar, or from under a piazza, where contamination is possible.