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the stove generally, and was pressed forward and upward by the current of cold air moving in that direction. The warmed air chiefly entered the first tube, and found its way out as shown on the drawing; the second and third tubes acting chiefly as inlets when intermittent air currents were once begun. The building was lit by electricity, the incandescent lamps being held by the iron ties of the principals. This hall was an illustration of the failure of silk valves for regulating the volume of air which the ventilator has to carry. They were disarranged when the ventilation of the hall was examined, and the latter, bad as it was, was much benefited in consequence.
In the case of a large and well-built school and classrooms, the assembly hall had a central louvre outlet below which the silk valves were arranged. When examined, these silk valves were large and closed so thoroughly that in consequence of their weight and the fact of the hall being proportionately low, the valves were rarely lifted unless the temperature of the air outside was below 450. During the spring and autumn months, if the temperature of the air outside was 5oo F. or more, they did not act at all, and the condition of the ventilation was bad in the extreme. The inside of the roof of the hall was carefully plastered, and there were few crevices or interstices in it, so that it was one of the most difficult halls possible to ventilate in moderately warm weather. Silk valves or valves of any kind should not be used in outlet ventilators for public buildings. Delicate valves are required in chimney breast ventilators, and the above remarks do not apply to dwellings. They do apply, however, to the classrooms of schools, as the reduced pressure in these rooms will not allow the use of mica, silk, or any other valves in the outlet shafts.
Fig. 18 is a rough sketch of a well-known place of worship in London. There are three ventilators on the roof, and the building is ceiled near the wall-plate. There
is a movable pane in each of the highest windows or lights on either side of the building, shown at A A, and as these lights are fixed about 1o feet from the ceiling, they are used as outlets for the foul air; but, in cold weather, half of those opened admit a flood of untempered and frigid air, which falls down and spreads out like a wet blanket for some distance around. On one occasion when the temperature of the air outside was less than 4oo F., the outlet window panes referred to were opened wide, but notwithstanding the most persistent attempts to admit air from the outside through the lower openings in the windows above the gallery, and through those beneath the windows under the galleries, the atmosphere in the building was in a most see-saw condition. At one moment deluges of cold air descended, and at another there was an upward movement which caused the air to be drawn through the window openings in thin, cutting streams, necessitating the neck and head to be protected by coat collars and other contrivances. Large box openings were made in the window sills, and these belched forth dense volumes of frigid air. There was no attempt to ventilate. A very little heated air from a stove or two underneath entered the building, and most of the heating was done by lighting the gas burners used for illumination some hours before the audience arrived. Although a large hall, seating 2,ooo persons or more, there was practically no provision for admitting warmed air near the ground level. The fact that this church was crowded Sunday after Sunday was most eloquent testimony to the ability of the preacher, because there was neither ventilation nor comfort for the majority of the audience. The church could be ventilated through the floor from the rooms underneath, but the present condition of the ventilating and heating is very bad.
Fig. 19 is a large building with seating accommodation for 1,2oo persons. It is of considerable height, especially in the centre, which forms a large dome, and this is crowned with one huge louvre outlet above the centre of the dome. During cold weather, air from the outside pours down the large opening under the louvre turret at intervals of a minute or less, according to the temperature of the air outside, upon the heads of the audience. The descending air is slightly though imperceptibly warmed by the gas flames over which
it has passed, and by the products of combustion with which it is mingled; for gas flames are used at the top of the dome immediately under the outlet to assist in forming an up current. The air coming in from the front doors forces against the current descending from the dome, and the air near the heads of the audience is pressed forwards in the direction of