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cupola was as much as 1,361,000 cubic feet for 736 places, equal to 1,848 cubic feet to a place. For the whole audience-room, containing 1,472 places, the total amount of air removed on an average during the five evenings in May, 1863, when the observations were made, was as much as 1,970,000 cubic feet, or 1,338 cubic feet instead of 1,060, which was all demanded. The total amount was even raised on December 3, 1862, to 2,121,000 cubic feet an hour.

137. Maintenance of equality of temperature in the different galleries.I have given in my investigations in regard to ventilation* the results of experiments which have been made under very different temperatures, and which have shown that the results obtained have exceeded what was required as to the amount of air removed from the room at the different galleries. The results relative to keeping up the temperature have not been less satisfactory. In fact, by means of this regular ventilation, the temperature at the different galleries has been maintained at a very remarkable state of uniformity, as shown by the following results for the first and fourth galleries, which alone will be

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It is well to repeat that in a place strongly ventilated a temperature of 75° does not feel unpleasant, and that if the direct external airopenings required for the summer season have been made it will be easy, if required, to obtain a still smaller difference between the external and internal temperatures.

At the old Opera, the Italian Theater, and most of the unventilated theaters, it is not unusual to observe temperatures of 95° and 105°.

138. Temperature on the stage.-When the heaters designed to warm the stage are well managed, a proper degree of temperature may always be maintained there. Thus, in November, 1863, with an external temperature of 390, was obtained

On the stage

In the orchestra-stalls

° F.

66.02

70.88

72.32

73.94

*Etudes sur la Ventilation, vol. 2.

In the gallery-boxes, (average) ..
In the amphitheater, (fourth gallery)

In May, with external temperatures of from 640 to 68° at 7 o'clock, and from 55° to 57° at midnight, the temperature on the stage was on an average 71° to 73°.

139. Volume of air carried off at the cupola to a cubic foot of gas burned.During the experiments of May, 1863, the volume of gas burned an hour in the main room was on an average 2,940 cubic feet, and the volume of air was 1,361,000 cubic feet, which corresponds to 462.5 cubic feet of air carried off by a cubic foot of gas consumed. But in the above-mentioned consumption is included that of a large number of burners which had no direct influence on the ventilation. A removal of 600 to 800 cubic feet of air to a cubic foot of gas directly consumed to produce it may be calculated upon when proper arrangements are made.

140. Consequences of the preceding facts.-The results of direct experi ment made in different seasons show that the arrangements adopted for warming and ventilating the Lyric Theater are capable of producing satisfactory results. The same is true of the Gaîtés.

It is a pity to see the public, in consequence of the senseless parsimony of the manager of a theater, deprived of the advantages which the administration of the city of Paris has, at considerable expense, undertaken to secure them.

STABLES AND COW-HOUSES.

141. The capacity of stables should be 1,800 cubic feet to each animal; this was the proportion adopted in 1841 by the war-minister for cavalrystables. In all constructed since that time for the army-service, the width allowed for each horse is about 43 feet.

This increase of space produced from 1835 to 1858 a reduction in the number of horses lost in 1,000, from 51 deaths by glanders in the periód from 1835 to 1845 to 10 only during that from 1845 to 1858, and from 94 deaths from all diseases in 1835 to 1845 to 22 only from 1848 to 1858.

Large corporations, such as the General Omnibus Company and the railroad-companies, are then wrong in restricting the capacity of their stables to 700 or 900 cubic feet of air to a head.

142. Permanent opening of doors and windows.-Experiments carried on for several years in cavalry-regiments in garrison in the north, center, or south of France, have proved that horses have better health and greater strength when kept in stables where the doors and windows are constantly kept open night and day in all seasons than where they are kept shut. Similar observations have been made in stables containing a great many cattle, which are thus relieved from epidemic affections of the respiratory organs.

143. Amount of air to be allowed.-When stables are not arranged so as to admit air throughout their whole length and by two opposite walls, it is proper to make in the roof at the middle of the alleys, if they are double or above the passage behind the horses, ventilating-chimneys of brick sufficiently large to secure a ventilation of 6,400 to 7,000 cubic feet

of air an hour to a horse, with a velocity of 28 inches a second, which may be produced by a difference of temperature of 110 to 13° between the external air and that of the stable. This requires that the chimneys have a sectional area of 108 to 124 square inches to a horse.

By means of this ventilation, the hygrometrical condition of the air in the stable will be maintained within convenient limits.

144. Use of gas-burners.-The ventilation of stables may be increased by making use of the heat given out by gas-burners used to light them up at night, which then allows of reducing the sectional area of the ventilating-pipes.

145. Cow-houses.-What precedes relates to work-animals. In the case of milch-cows, it appears that a certain drowsy laziness is favorable to the production of milk; and in such cases it is necessary to limit the ventilation to what is absolutely necessary for health.

MEANS OF CONTROL.

146. Means to be used to determine the condition and the results of a system of ventilation.-It has been shown by the numerous examples that precede that the establishment of a complete and regular renewal of air in occupied places in reality presents no difficulty, and that the rules to be followed are very simple. Their application will be equally so, and will involve but little expense if architects take care to devise plans of ventilation at the same time that they make the plans for construction, instead of waiting till the building is almost finished.

But when all the arrangements have been made to secure the renewal of air, the first thing to do is to examine whether the desired results have been obtained, and the second is to regulate the operation of the apparatus.

To determine what are the amounts of air carried off and drawn in, a small portable instrument is used, called an anemometer, consisting of a wind-mill with light and easily-moved vanes, connected with gearwheels and pointers, which indicate the number of turns made by the vanes in a given time.

Experiments show that with an apparatus of this kind the velocity of the air may be deduced from the number of turns of the wings by means of an equation of the form :

V = a + b N

V being the velocity in a second;

a, a coustaut term, expressing the velocity of the air at which the instrument commences to move;

b, a constant number;

N, the number of turns indicated in a second.

Thus, one of the anemometers of the Conservatory has the formula: V (in inches) 8.66 + 7 N

=

This instrument should be placed, as far as possible, in a part of the flue traversed by the air, where the velocity is uniform and well regu

lated. It should be kept in operation at least two minutes, if a watch indicating seconds be used; and four or five, if a watch indicating minutes. only is employed. From the number of turns made in this interval of time may be deduced that corresponding to a second, whence the velocity, V, may be obtained. This velocity, multiplied by the sectional area of the flue, will give the amount of air passing through in a second, and from this the amount passing through in 3,600 seconds, or an hour, can be obtained.

If it be feared that the velocity in the flue is variable, on account of its large size or other circumstances, it will be necessary to try the instrument at different places, which will then give with sufficient exactness the mean velocity of the air.

When it is desired to determine the volume of air which is carried out or drawn in through an opening covered with a grating, the anemometer should not be placed above or in front of this opening, as is done by many observers, and the velocity resulting from the number of turns observed taken as the mean velocity of the air passing through. Serious errors will result from this method. The proper way is to place before the opening, and fitting to it as closely as possible, a pipe having at one end the form of the opening, and joining at the other end a cylindrical pipe at least 2 feet long, in which the anemometer should be placed, which would then indicate the velocity of passage in this part of the auxiliary pipe. The velocity of the air introduced or withdrawn in a second or an hour may easily be deduced afterward.

147. Means of insuring the regularity of the ventilation.-While the use of portable anemometers serves for experimental investigations and for the determination of the results obtained by the ventilation, it is not sufficient to secure the necessary regularity of ventilation in large establishments.

In such cases it is necessary to introduce much larger anemometers, connected with an electrical recording-apparatus placed in the office of the superintendent, or in a conspicuous place where it can be seen every hour, or every morning and evening, whether the renewal of air is proceeding with regularity and with the prescribed energy.

This is not the place to describe the apparatus.* I confine myself to stating that an anemometer of the kind has been employed with suc cess for several years at the Conservatory of Arts and Trades, to insure regularity in the ventilation of the lecture-rooms; and that every year it works for about five consecutive months without derangement, and without requiring any care but the renewal of the solutions in the battery two or three times a season.

A similar anemometer has been in constant operation for several months in the ventilating-chimney at Lariboisière Hospital, and has served to show, every morning, the amount of foul air removed from a

See the Annales du Conservatoire, vol. 5, 1864, p. 341.

wing containing 106 beds, during the night, and, every evening, the amount during the day.

Methods of observation of this kind, automatic and independent of the personal action of the employés, are the indispensable adjuncts of great ventilating systems, if it be desired that the service be performed in a regular manner. They also serve to render the work of inspection by the heads of the establishment more easy and efficient.

Errata in previous portion of this article contained in the report for 1873:

In § 31, pp. 308, 309, for 1,000 cubic feet weigh, read one cubic foot weighs; and for weight of 1,000 cubic feet, read weight of one cubic foot.

In § 35, pp. 310, 311, for 0.0000756, 0.000081, 0.000005, 0.000077, 0.000074, 0.000003, read 0.0756, 0.081, 0.005, 0.077, 0.074, 0.003 respectively.

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