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vitiated as to be unfit for inspiration. For school classrooms and lesser halls, the windows are made to open, and various well-known devices for blocking the sills and for shielding the lower sash when it is raised two or three incheSj have been advocated and tried, Fig. n. These are useful when the temperature of the outer air is 55o or more, but they are only a makeshift at the best in cold weather.
It is desirable to consider the condition of some of the Board Schools in slight detail, because in reference to the ventilation of these the architect is advised by the Education Department. As already noted, 2J inches of inlet air-space is the minimum advocated for each scholar, in addition to what leaks in around windows and doors. As the windows open generally, or a portion of them, a considerable volume of air is admitted in this way. But where fires are used in the classrooms, the cold air falls over the coldest material, and down beside the coldest and outer walls, and the 2J inches of inlet air-space are generally furnished through the outer walls also. If the fire is in the centre of the interior wall—the best place for the chimney to draw—then the children near the windows are much too cold, and those near the fire too warm. But the worst feature is, that nearly all the inlet air, instead of rising up to the level of the children's heads, flows along the floor of the room during cold weather, for the most part in a stream not more than 18 inches deep above the ground level, giving the scholars cold feet and legs, but little fresh air to breathe. It is a fact, however, the Education Department recommends that each classroom shall have one or more outlet shafts, and that these be carried up by the side of the chimney flue from the fire heating the room. By this arrangement the walls of the outlets will be warmed and so create a stronger current. Under the circumstances it may be concluded that the inlet air must ascend and be inspired by the children because the outlets begin above their heads. Unfortunately, this argument, so convincing in theory, does not hold good in practice, except, perhaps, for a few weeks in the aggregate during the year. When the temperature of the air outside is below 5o0 it is found that if enough air is let into the classroom to feed the fire and still allow the foul air to pass through the outlets it is impossible to keep the room sufficiently warm; and, as a bright fire is maintained then, the smoke and air are hotter in the chimney than the foul products in the air outlets, and little or no air ascends the latter. Furthermore, for want of proper arrangements at the mouth of the outlets, and sufficient velocity in the foul air shafts, the very moment they cease to give an up current, cold air from above descends the outlet shafts until it gets warmed and expanded, when it rises again. The cold air may fall 1o or even 2o feet, according to the height of the outlet flue, become warmed, and rise upwards, so forming intermittent air currents which further tend to make outlet action impossible. It may be concluded as a general axiom that where fires are used for heating, and no other provision made for warming the inlet air, the fires cannot keep up the temperature in cold weather when there is enough air admitted to furnish some for the foul air outlets. When the air is above 5o0 outside, it may be assumed that the windows can be opened so as to increase the pressure upon the air in the classroom, but if this is done in windy weather, the powerful action of the outlets during every lull in the blowing of the wind so pulls upon the air in the classroom while the blast of the next gust of wind lasts, that if the wind aspirates upon the openings in the windows the fire is caused to smoke. By arranging valves in the fireplace, just above the fire, so as to reduce largely the volume of air going up the chimney, it is possible to make the foul air outlets more effective, and this ought to be done.
Where children are educated by the million in public schools, no excuse exists for such discomfort, rheumatism, neuralgia, cold in the eyes, and other ills from which the children too frequently suffer; and a better state of things ought to prevail. Indeed the Education Department should be in a position to demand that every school, newly erected, shall be heated by hot water pipes only, kept at a temperature of about 15oo F.; that the outer walls shall be warmed, and all inlet air of a temperature below 550 F. before it gets into the building; that proper outlets be provided, and the currents in them assisted either by heat or by fan action. In this way 5oo cubic feet of air per hour per scholar can be provided.
For hospitals and barrack dormitories, where there is sufficient margin near the outer walls, cold air inlets may be used judiciously; and, as the beds are not near the floor level, it is not difficult to do this without causing draughts. Owing, however, to the vagaries of the wind it is most advisable to subdivide the surface of the inlets greatly in all instances, because it will be found that inlets of a superficial area of only 16 square inches have a peculiar knack of sending a stream of cold air a long distance wlien the outlets are aspirated by the wind.
As the warming of the inlet air is frequently attempted, it will be well to consider the matter at this stage. Many churches and buildings are heated by hot water pipes sunk below the floor level in the aisles; and in some cases hot water pipes are carried along the walls above the floor level as well. Referring first to hot water pipes fixed below the floors, it frequently happens that openings every ten feet or more perhaps of the length of the building convey fresh air through gratings in the outer walls to the trough in which the hot water pipes are laid. Owing to the difficulties which the distribution—or want of distribution—of the inlet air along the pipes between the air inlet channels entail, the cold air usually rushes up just above the point where the fresh air channel joins the hot water pipes, and, for the most part, unheated. When the weather is very cold the result is disastrous, as the frigid air rushing up flows right and '?ft giving rise to intolerably unpleasant air currents. In some cases perforated zinc has been used to prevent the air coming up in a deluge at one place, but owing to the difficulty of keeping the sheets of metal flat, and preventing the nap from the cushions and other woollen matter filling up the holes, the full benefit of this most desirable method of introducing fresh warm air has rarely if ever been attained. Where a fair attempt has been made to properly distribute the incoming air along the whole length of the pipes, in nearly all instances there is too much top exit space in the roof to enable the air inlets to work satisfactorily. It has been shown already, that apart from the wind effects upon inlets and outlets, too much outlet space in comparison to the area of the inlets always results in the formation of intermittent air currents in churches and public buildings during cold weather. When there is an up current moving, the whole ventilating power of the building is brought into play, the result being that much pressure from the outside causes great volumes to enter through the channels feeding the hot water pipes below the floor. Even with fair distribution, the sudden pressure forces incredibly large volumes of air at the critical points where the fresh air inlets join the trough in which the hot water pipes are laid. If the temperature of the outer air is at 320 F. or lower, human nature cannot bear the inrush of frigid air, and the caretaker after one or two such experiences is so afraid to have a repetition that he closes the gratings in the outer walls which feed the fresh air channels, and so a most useful arrangement is rendered inoperative.
During the latter portion of the nineteenth century, the authorities of most Nonconformist places of worship adopted the hot air furnace for heating—the cold air in the building descending one grating, then passing over heated iron plates, and finally re-entering the building by another grating. In this metho'd of heating, provision was made for the introduction of fresh air, but the instances in the author's experience in which a large volume of fresh air was so heated, rose vertically to the upper part of the building, for the most part, and proved of very little use. When a building is to be heated by the hot air furnace, the advantage of shutting the top air outlets is manifest, but experience shows that very frequently the leakage around the valves of the ventilators and through the crevices in the roof is so considerable that, unless the heating during cold weather is commenced on the Saturday, the building cannot be warmed for the Sunday services. The caretaker soon realises that it is no use to send fresh air warmed into the building, because this simply ascends vertically at the end where the hot air grating is fixed, being forced upward by the cold air which descends from the roof at the other end. It is more than he can do to warm the air inside the building, and all his efforts are directed to closing every inlet and outlet so that the circulation of the air inside shall warm the walls. The caretakers are afraid to experiment, and if they do and fail, the complaints of the pew owners soon check their ardour, the result being that the fresh air provision is very rarely used. Nor are the caretakers to blame, as the ventilation and heating of the building should be placed beyond the experimental stage before it is given into their charge. The hot air furnace is not to be recommended, because if the air inlets are opened, and fresh warm air admitted in large volumes, it will be found that in nearly every instance cold air will fall from the roof at the other end driving the heated air out in a perpendicular current. Again, the action of wind currents either upon the ground level where the fresh air inlet is situated, or upon the outlets in the roof of the building, will cause intermittent air currents inside, and greatly interfere with the ventilation. The author watched