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February 1,18CS. , THE CIVIL ENGINEER AND ARCHITECT’S JOURNAL. 35 vitiated air. In the case of the theatre shown in the drawings, the inlet for fresh air is made in the square of the Tour St. Jacques, by means of a 11J feet diameter, communicating by a tunnel A of the same area -with the space underneath the theatre, Fig. 9, where the warming apparatus and the mixing air chambers are situated. The velocity of the current in the inlet passage A was ascertained to be 3’08 feet per second in a special examination that was made some years since, and the sectional area of the passage being 97 square feet, the volume of fresh air admitted amounted to 300 cubic feet per second, which was somewhat in excess of the quantity that the appa ratus was designed to supply. This area of inlet however has subsequently been allowed to be contracted considerably by the growth of ivy at the entrance. The admission of the fresh air to the body of the house from the main supply shafts P P, Fig. 8, takes place between the floor joists or through the false bottoms made under the floors of each of the rows of boxes and gallery, as shown by the arrows at B B, Fig. 9, the air entering horizontally all round the theatre through these spaces, which should not be less than 5 to 6 inches clear height. The fresh air is also admitted by openings from about 10 feet height in the vertical walls on each side of the stage, and also by auxiliary channels under the flooring of the passages, intended specially for extra sum mer ventilation, and controlled by valves. For preventing the occurrence of unpleasant draughts upon the opening of doors into the exterior passages, these passages have to be warmed to a temperature of about 68°, and inlets of warm air are pro vided opposite the different doors in the passages. A portion of the air, on entering by the main inlet passage A, Fig. 9, is warmed by traversing two sets of heating appa ratus C C placed in the basement; and the remainder is deli vered into mixing chambers for regulating the temperature of the air supplied in the building. The area of passage through the heating apparatus is 97 square feet, and the volume of warm air supplied is 245 cubic feet per second, giving a velocity of current of 2'5 feet per second. The vitiated air is taken off through numerous openings in the lower part of the sides of the boxes and passages, and in the risers of the steps in the gallery, each.box or pair of boxes having a separate discharging flue ; and the total area of these openings has to be such as to allow the velocity of the air not to exceed 2'3 to 2'6 feet per second. The exhausting flues E E from the several tiers of boxes are made to rise towards the dome F above the chandelier, while those from the pit, orchestra, and boxes on the ground tier are carried below the floor into main flues leading to the vertical shafts G G; and the area of these exhausting passages should be such as to give a velocity of current of 3'3 to 3'9 feet per second. In the pit and orchestra, outlet gratings should be placed allround the sides, and in the sides of the air passages underneath the seats; these outlets open into the space left under the floor, which leads to the main exhausting shaft G on each side, this space being divided accordingly into portions by the central partition J. The outlet gratings should not be placed in any case in the floor, as was done in this theatre, contrary to the writer’s in tention. The cast-iron chimney pipes 11 from the heating apparatus are carried up the exhausting shafts G to aid the draught, the pipes being kept isolated throughout; and a small fire grate H is placed at the bottom of each shaft, for use when extra ventilation is required in summer. The area of the ex hausting shafts G G is required to be such as to give a velocity of current of 5'6 to 5'9 feet per second; and they should lead, when possible, to the dome F over the centre of the theatre, into which all the outlet flues from the upper tiers of boxes also discharge. The general outlet shaft K above this dome should be built of brick, not metal, and should be carried at least 20 or 25 feet above the top, its area being such as to give a velocity of current about 6'6 feet per second. A series of experiments on the ventilation were made on five successive nights in May, 1863, with the external temperature ranging between 56° and 74° ; and the result obtained was that with an average consumption of 4 cwts. of coal per night, cost ing 7s. to 8s., the removal of 166 cubic feet of air per second was effected, amounting to 1400 cubic feetof airper hour per seat of the pit and orchestra. With this ventilation the temperature of the house can bo maintained within comfortable limits; but this extent of ventilation is not actually employed, as the intended use of the two large exhausting shafts G G is not carried out. The experiments made at the same time on the ventilation of the boxes showed that an abstraction of 377 cubic feet of air per second was effected by the centre shaft over the dome, amounting to 1800 cubic feet per hour per seat. The actual average ventilation for the whole house during the five even ings was found to be 1330 cubic feet per hour per seat. By this uniform ventilation the temperature in the different rows of seats was maintained most remarkably constant, the average tempe ratures in the first and fourth tiers being 68° and 70° respec tively, when the external temperature was 52°; and when the latter was 70 c , their temperatures were 78° and 80° respectively, in other large theatres, however, which are not so ventilated: these temperatures are not unfrequently as high as 95 Q to 105°. At another trial in November 1683, when the external tem perature was as low as 39°, the temperatures within the house were found to be maintained at 66° on the Stage. 71° in the Orchestra Stalls- 73° „ ,, Boxes. 74° „ „ Gallery. The above results show the satisfactory manner in which the mode of ventilation that has been described effects the objects intended ; but the full benefit of these results is unfortunately not received in the present case, from the arrangements being only partially carried into regular use; and it has to be re marked that however perfect the ventilating arrangements may be in the construction of a building, it is indispensable that the working of them should be under the constant charge of pro perly qualified and responsible management, in order to ensure the desired object being systematically attained. The President said they were greatly indebted to General Morin for the valuable facilities afforded by him for the present Meeting in Paris, as the Director of the Conservatoire Imperial des Arts et Metiers. The efficiency of the system of ventilation carried out upon the principles advanced in the paper, was practically illustrated by the agreeable condition and temperature of the air at the present moment in the Lecture Theatre, notwithstanding the number of persons now assembled in it on a summer day. Mr. Edwin Chadwick remarked that the two opposite systems of ventilation—the one by propulsion or driving in the air by mechanical means, and the other by suction or creating a draught by heating the air in the discharge flues—might both be seen in operation in Paris, in different wards of the Lariboisiere Hospital near the Northern Railway Station; there had been considerable controversy respecting the relative advantages of the two plans as carried out in that building, and he did not know of any better practical example of the two methods. The fresh air supplied by propulsion was warmed, and driven in by engino power by means of a fan; and in abstracting the vitiated air by suc tion, it was taken off close to the points of greatest vitiation, namely between each of the beds in the ward. From a careful examination made of the subject by physicians he had been led to conclude that the system of suction, as described and advocated in General Morin’s paper, was not only the most economical, but also the best in regard to the degree of purity maintained in the air of the building, as the system of propulsion was found to be attended with the disadvan tage that the current of fresh air driven into a room would sometimes pass through direct to the outlet, without thoroughly expelling the vitiated air and thus allowed an objectionable accumulation of vitiated air to take place in particular portions of the room. The arrangements for ventilation by suction at the above hospital had been developed and carried out with very decided success by the late M. Leon Duvoir, who had undertaken to give a supply of 2000 cubic feet of air per hour for each bed in the wards, heated to a uniform tempe rature of 60 deg. Fahr., at a charge of Id. per bed per day; and the actual cost he understood had been found to be only about half that amount, the price of the coalsused being about 40s. per ton in Paris at the time. The rarefaction necessary} for effecting the ventilation was obtained by means of a hot-water tank at the top of the building, and the ends of the air flues being carried up through this tank by means of thin iron pipes, an upward current of air was established by the heat ing of the air within the flues, whereby the vitiated air was abstracted from the building with a uniform draught, as tested by holding a lighted candle at the bottom of any of the air-flues. In some cases the vitiated air was taken off upwards, and in others downwards, and the ventilation was effected with complete success in each way. For the purpose of saving heat, a coil of water pipes or a water jacket was placed round the chimney of the furnace employed for heating the water in the hot water tank, and by this means nearly two-thirds of the heat escaping into the chimney was found to be saved. The fresh air admitted to the building was warmed by being made to pass between a number of thin iron pipes containing the heated water supplied to the
