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thiee fresh air inlets on each side of the church connected to the lines of pipes, but owing to the intermittent air currents in the building they were kept closed. The gratings above the pipes in the church were excellent, and nearly three feet wide, but more than two feet of this was covered with close Kidderminster carpet which prevented the circulation of the air through the grating, and reduced the heating effects of the pipes by at least one-half their power. Furthermore, on removing this carpet and raising one portion of the grating, the hot water pipes were found to be covered with a coating of fine woollen down, nearly half an inch thick, which further reduced the heating value of the pipes. When the temperature of the air outside was above 5o° F. there was no appreciable down draught, and, for the most part, the air leaked from the roof without giving rise to perceptible movements, whilst the ventilation seemed to be fairly good. The church was lit by a large central gaselier at B. The ventilation of this church was top heavy, that is, the outlet spaces in the roof were too many, and the cracks between the match-boarding required to be partly closed. Then the air from the fresh air inlets wanted more careful distribution, and the hot water pipes to be kept clean. The carpet was removed, and it was possible to render the ventilation good, and the building comfortable for the audience, without making much structural alteration.
Fig. 14 was a large public hall seating 1,5oo persons. It was ceiled some 4o feet from the level of the ground floor, and was at least 6o feet high to the top of the roof. The building was lit by three large sun-burners whose exit tubes were surrounded by spacious cylinders several feet in diameter. When the tubes and cylinders were open in moderately cool weather, the area of the outlet space was much in excess of that of the inlets. At a concert the author attended, and watched the air currents, the principal tenor came to the platform in his overcoat with the collar carefully
raised around his neck to shield it from the draught. The night was very cold, and owing to the down draughts the movements of the air were sufficient to cause an anemometer to revolve continually while lying on the seats of the orchestra. The fault was not due entirely to the arrangements for ventilating and heating, and was soon partly remedied, but the spaces around the valves in the cylinders and the sizes of the outlet tubes above the gas burners were much too large to work properly in cold weather. There were three coils of pipes on either side of the building and two in the corridor leading thereto, whilst two coils were fixed on either side of the gallery which ran on three sides of the building. Fresh air inlet gratings faced each coil, but the area of these in the aggregate was much less than that of the outlet spaces. It will be seen from the drawing that Nos. 1 and 3 of the outlet tubes permitted great volumes of cold air to descend, and No. 3 acted invariably as an inlet. The main entrance was at B, and when the door was open, the pressure of the air going in under the gallery caused the centre burner to act powerfully as an outlet. When testing the volume and action of the intakes behind the coils, A A, of hot water pipes, it was noticed that the instrument stopped for an instant, then reversed and stopped again for some seconds. Thinking something was wrong with the instrument the tests were repeated, but with the same results. A pressure gauge which was placed in another part of the building was watched, when, to the author's astonishment, it registered more pressure within than there was outside the building. As the instrument registered the same excessive pressure at intervals of about a minute, and the instrument was observed at frequent intervals, there was no doubt of its accuracy. Further experiments showed that the building, which was very high, had a large excess of outlet area in comparison with that of the inlet. The outlet space was so considerable that the tubes over the sun-bumers, 1 and 3, nearly always acted as inlets, and that for a second or two every minute cold air poured down No. 2 also. After a deluge of cold air had descended, it became warmed, and a powerful up current was formed in No. 2, whilst No. 1 sent out much air, and No. 3 did not let in quite so much. When the up current ceased somewhat, and the velocity in the outlets weakened, great volumes of cold air descended, and this being so cold and heavy, and falling through so great a height, 6o feet or more, compressed the air in the building so much that, in consequence of the elastic nature of the air, the pressure inside the building actually exceeded that of the outside air for some seconds. When the upward movement began again, it proceeded so rapidly that No. 2 burner flared greatly and became partly nonluminous for some seconds. The intermittent action of the air currents in this hall is already referred to on page 15.
The ventilation of such a building would be much improved if the outlet space was under proper control, even with the arrangements shown, and the air inlets provided; but it is almost impossible to get the warmed air to travel from the sides to the centre of a wide building, and it was suggested that a hot air grating should be provided throughout the length of the centre of the hall.
Fig. 15 was a large chapel seating 1,ooo persons. It had galleries, but these are not shown. There were two sunburners and ,a central opening, D, in the ceiling to afford additional outlet for the foul air in summer. The building was ceiled at the wall plate, and about 33 feet high to that point. After new sun-burners were erected, a severe down draught was experienced, but the gas flames gave little indication of the sources from which the cold air descended. It was found, on examination, that there were air spaces around the tubes of the burners and very considerable interstices around the central opening. These poured down large volumes of cold air when the outside temperature was low, giving rise to most unpleasant draughts. The chapel was