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and there will be three ventilating-flues, 100 square inches in sectional area, or 84 x 12 inches.

The vertical flues should be carried uuder the floor of the ground. story, and joined to the first horizontal collectors intended to furnish passage to the air brought by the first, and each should carry off 12x.78= 9.36 cubic feet a second with a velocity of 3.28 a second. They should

9.36 0 then have a section of ... =2.86 square feet, or be 1 foot 8 inches square, for example.

One of these flues, which would also ventilate the two single-bed bed. rooms, or 14x.78=10.92 cubic feet, should have a sectional area of 10.92

=3.34 square feet, or should be 1 foot 8 inches by 2 feet. If these pipes do not lead directly to the foot of the chimney, and if the general arrangements adopted render it necessary to carry the first collecting-pipes into a second collector, the volume of air which the latter will be obliged to pass will be 50 x.78=39 cubic feet, with a velocity of 4.6 feet a second. Its transverse section will then be equal to 1 = 8.50 square feet, and it may have the dimensions 2 feet 10 inches by 2 feet 10 inches.

If the main ventilating-chimney should have to carry off the foul air of both wards, or that from 100 beds = 280,000 cubic feet an hour, or 78 cubic feet a second, with a mean velocity of 6 feet a second, its internal sectional area should be =13 square feet, and its mean internal diam. eter 4 feet. At the upper part, this diameter should be reduced to 3 feet 10 inches to make the velocity there 61 feet a second.

91. Introduction of fresh air.—The openings for the introduction of warm or cold air should always be placed near the ceiling, and distributed as uniformly as possible throughout the whole extent of the halls in the proportion of one to every two beds if possible, or at least one to every four beds.

When they are made in the walls, they should be furnished with registers in the form of slats inclined 200 or 250 to the horizon in order to force the air in that direction toward the ceiling.

The transverse section of the vertical or other flues should be calculated so that the air will traverse them with a velocity not exceeding 3 or 4 feet a second. That of those through which the air flows immediately into the room should be determined by the condition that the entering velocity should not exceed 3 or 4 feet a second.

In the case where the air flows from above vertically downward, through openings in the ceiling itself, which may take place where double floors are used or where a loft serves as an air-chair ber, the sum of the clear sectional area of the passages shonld be calculated on the condition that the velocity should not exceed 18 inches or 2 feet a second.

When ordinary heaters are used for heating, the warm air which they supply should be introduced before its admission into the halls into a mixing-chamber, where a sufficient quantity of external air is also admitted, in order to moderate as required the temperature of the air supplied to the rooms.

To secure the proper mixture of external air with the warm air from the heating apparatus, it will be necessary to keep the fresh air above the current of warm air by means of more or less wide partitions. It will then happen that, as the first or denser stratum tends to fall while the second or lighter stratum rises, the mingling will necessarily take place. This applies as well to separate and direct openings for the admission of warm and fresh air in balls as to those for the admission of air into the mixing.chambers. The partitions should be made of brick laid flat, and be at least two inches thick.

During the period of fires, the temperature of the inflowing air should, for healthful ventilation, differ as little as possible from that intended to be kept up in the balls, which should be uniformly about 60°.

The mixing-chambers should be formed either in the floor above the the heaters or in the corridors or small rooms.

Registers should be placed in the mixing-chambers, to permit the temperature of the air supplied by them to be regulated at will.

Similar arrangements should be made when hot-water or steam heat. ing-apparatus is used.

If the hospital stands by itself and is in a healthful location, the external-air supply may be taken either at the ground-level from the middle of a lawn or flower-bed, as at Vincennes and the lying-in hospital at St. Petersburg, or at the level of each floor.

Descending currents will not be required to carry the air from a cer. tain height, except in cases where the proximity of more or less unbealthful buildings would lead to the fear of infection in the air at the ground-level.

In that case, thở chimney for bringing in air should be placed as far as possible from that for carrying it off. The sectional area of the former, and in general that of all external openings for the admission of air, should be calculated so that the velocity of admission should not exceed 2 feet a second, in order that the dranght produced in the vicinity of the openings may only extend a small distance.

The openings for the admission of air entering at a considerable height should be provided with valves or doors, wbich may close them if re. quired.

In summer, when the action of the draught in drawing in fresh air is pot assisted by the increase of temperature which the heating-apparatus gives to the fresh air in winter, there should be made in the walls, especially on the faces exposed to the north or the east, auxiliary openings siwilar to those previously mentioned, and capable of being opened or closed at will by means of internal valves furnished with self-closing springs.

As the air thus introduced may be too cool at night, it is necessary that it should be directed from the lower part of the room toward the ceiling, and that its velocity at entrance should be about 2 feet a second, in order that it may be rapidly diminished before it arrives at the escape-openings.

The regulating-apparatus connected with the registers should be so arranged as to be exclusively under the control of those in charge of this service.

When any arrangement for ventilation on the exhaust system has been carried out, it may easily be determined by direct experiments easily made in the main ventilating.chimney, or, if desired, in the separate flues, whether the prescribed amount of air is really drawn off, and what is the corresponding excess of temperature in the chimney over that of the external air; and if with this excess, which usually will not vary, as has been previously stated, much from 350 to 450, the ventilation be found sufficient, it will then only be necessary to regulate the heat in the chimney so that its temperature will always exceed by the same amount that of the external air. .

92. Arrangements for ventilation in summer.- When the main halls of the hospital are warmed at the same time by general heaters and by fire-places-of which latter the ventilating fire-places described in § 13 should be preferred, as they at the same time carry off foul air and introduce a considerable amount of fresh air properly warmed-openings for the admission of fresh air should be made in addition to those of the ventilating-chimney, and arranged, as has been described, for summer-ventilation.

Stairways, waiting-rooms, and other places giving access to the halls should be heated to a temperature which, especially for the latter, should be at least equal to that of the halls. In this way, their effect in producing draughts of air will be diminished. It would be well, then, to put up heaters in these places even when fire-places are used in the main rooms.

93. Use of the heat given out by the lights.-In hospitals lighted by gas, it will be well to assist the draught by means of the heat given out by the burners, which plan will have the double advantage of rendering the ventilation more energetic, and of removing the unhealthful products of combustion. This should especially be applied in the case of waterclosets, which should have double doors opening from without inward in the direction of the draught.

The kitchens and the privies of hospitals should be removed from the hospital proper, and ventilated by a powerful current similar to those which will be described hereafter for such places.

94. Dispositions to be made in case of crowding or epidemics.- When the draught is produced by a circulation of warm water or steam, the energy of which cannot be increased much beyond its normal rate, it will be advisable to place gas-burners in the main ventilating-chimney, to be lighted only when a temporary overcrowding or the fear of epidemics renders tbeir ose necessary.

The number of burners and their consumption of gas will be calculated on the approximate basis of 500 cubic feet of air removed to each cubic feet of gas burned.

This auxiliary means is not economical, and should only be employed in exceptional circumstances.

ASYLUMS.

95. Asylums, designed for the old, insane, or infirm, do not require, for salubrity, as much ventilation as hospitals.

A renewal of air at the rate of 1,000 cubic feet of air an hour for each individual during the day and 1,400 cubic feet at night will be sufficient. It will then only be necessary to adopt the plans and the dimensions which have been given in detail for hospitals.

For heating during the winter, if the rooms are not very large, venti. lating fire-places should be used, which will also secure the renewal of air. But for spring, summer, and autuinn, it will be necessary to have recourse, for the removal of foul air, to the use of a ventilating-chimney and the arrangements before mentioned.

CHURCHES.

96. The great size of churches, the constant opening of their doors, the extent of glazed windows-always imperfectly closed-the openings in the vaults for the suspension of lamps or draperies and for the passage of bell-ropes, seem in general to render unnecessary the adoption of special arrangements for the admission and the removal of air, and reduce for the winter the question to that of warming.

For the churches of large cities, frequented at many hours of the day, it seems economical to keep up an active fire, constantly, day and night. Either hot-air heaters, with chambers for the admission of cold air, or bot-water heaters, may be used. The first suit more particularly the small churches, where a single heater, placed about the middle of the building, will suffice. The second, which carry heat to great distances, and give, besides, a more equable temperature, should be preferred for large churches. They have, in addition, the advantage of being readily adapted to ventilate certain attached places, such as catechising-rooms, where the air is constantly vitiated by the presence of many children.

What is most necessary to warm in churches is the floor itself. For this purpose it would be well to make the hot-water pipes branch out under many parts of the floor, and limit the number of fresh-air openings. This arrangement is similar to that of which traces are found in Roman constructions.

The air to be warmed by the heaters is taken from outside. A sufficient number of pipes in the aisles and passages admit the air through numerous openings placed in the vertical faces of the walls, or in the bases of the columns, a little above the floor, and not at the floor-level, as is often wrongly done.

During the sunmer season, the interior of churches, strongly heated during the day by the action of the sun on the roof and through the large windows, is often uncomfortable to stay in, especially in the morning. It would be easy to avoid this trouble hy arranging a number of windows to be opened at night, in order to admit the fresh air, and to be shut in the morning. The interior, thus cooled during the night, would be less warmed during the day.

These precautions, much neglected in France, where the heat of sum. mer seldom proves unpleasant, are regularly carried out in Rome, where it lasts a long time. A rule of the custodians of St. Peter's requires that the windows of the upper galleries be opened every evening in summer and closed every morning.

What precedes only applies to ordinary churches ; but in the case of chapels or subterranean churches, the interior height of which is very limited and which are often occupied by a large number of worshippers and fully lighted up, it becomes necessary to secure the renewal of air and the removal of the hot gases arising from the lights. The plans proposed in § 64 for night drawing-schools should then be adopted, producing a renewal of air at least five or six times an hour.

In churches where great ceremonies require the use of large canopies, preventing the circulation of the air, and in which a great number of candles occasion often an extraordinary elevation of temperature,* it is very important that the construction should allow of forming, in the upper or lateral portion, as many openings as possible in order to allow the external air to flow in with a velocity which will be less the greater the number of these openings and the more uniformly they are distributed. In this way will be avoided the at times unendurable currents of air produced by the doors and the elevation of temperature.

In winter, at the time of thaws after great cold, especially in the north, there is produced on the walls, and still more on the ceiling, is condensation of vapor, which often produces a sort of rain that affects the paintings. In such cases, it would be well to carry the warm air supplied by the heaters at about from 1400 to 1750 directly to the upper part of these edifices at the springing of the arches, in order to keep the vapor arising from the people in the lower portions of the church from condensing.

RAILROAD-STATIONS. 97. As an example of cases where it is proper to act contrary to the general rules given before, we will specify the methods to be adopted for

* In a great funeral-ceremony at Notre-Dame, Paris, the heat was such that the was. tapers began to melt.

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