or gas-burners which they contain, which often produce a degree of heat in excess of that necessary to warm the room.

The general rule, which requires that the foul air should be drawn off near the floor, cannot be exclusively followed without causing currents of air heated from 85° to 950 to fall upon the students. It is, then, necessary to carry away the hot gases, the products of combustion, through the ceiling. But at the same time it is necessary to admit the fresh air, which in that case must be cool, at a certain height as far as possible from the floor.

But if the same room should also be occupied during the day as a study or drawing-room, and if it were then ventilated according to the usual rule by drawing the foul air off near the floor, it would be well at night to maintain that ventilation in order to assist the circulation and the descent toward the floor of a part of the fresh air brought in, of which to make up for the heating-effect of the lights, there should be a much greater amount than during the day.

Observations made in a school of design in Paris attended every evening by 200 to 240 scholars, and lighted by 90 gas-jets, consuming together 320 to 350 cubic feet of gas an hour, led for this special case to the following rules:

1. During the day, regulate the amount of foul air drawn off at the floor-level to about 530 cubic feet for each adult scholar and admit the fresh air near the ceiling.

2. For night-sessions, make escape-openings in the ceiling, the clear area of which should be calculated at about 88 square inches for every 1,000 cubic feet capacity of the room.

If there is no loft above the room in which the ventilating-pipes can be carried, special pipes may be placed at convenient points, removed as far as possible from those at which the fresh air is introduced. These pipes should be supplied with convenient valves, in order that they may be closed during the day, and the amount of the hot gases removed at night regulated.

3. Place in the two opposite walls of the room, or at least in one of them, at the height of 10, 13 feet, or higher, if possible, as many freshair openings as convenient, each supplied with a regulator to direct the air horizontally near the ceiling, the dimensions of these openings being calculated so that the volume of air admitted may be increased to six or eight times the total cubical capacity of the room, with an entering velocity of but 2 or 3 feet a second.

By means of these arrangements, drawing-schools may be made comfortable at night, which at present are almost like furnaces, and in which it becomes necessary to open some of the windows even in winter, notwithstanding the discomfort which may be experienced in conse quence by the scholars nearest to them.

In the drawing-school just mentioned, the total amount of air carried off every hour was:

which corresponds to a total renewal almost eight times an hour.

By means of this active ventilation, the temperature in the room has been maintained till 10 o'clock at night at 67° to 70° at 5 feet above the floor, and at 750 on an average at the ceiling, while, before the introduction of the means of ventilation mentioned above, it was, respectively, at the same heights, 800 and 90°.

65. Plans to be adopted in schools already built.-It too often happens that no plan has been provided in schools, and especially in night-schools, to produce even a partial change of air or to regulate the temperature, so that a stay in them is as unhealthful as it is unpleasant. There is, then, as we have said, no resource but to open the windows, and this is both uncomfortable and injurious to the scholars seated near them. These defects may, however, be removed, at least in part, in most cases by adopting the arrangements described in § 64 in the case of a drawingschool.

In order to carry off the hot gases arising from the lights, and prevent them from affecting the scholars, ventilating-openings should be placed near the ceiling. A number of ventilating-flues should be cut, the size of which may be calculated by the preceding rules; if possible, making them so large that the air may be renewed four or five times an hour. If, however, it is only possible to make one flue, it should be connected by means of a horizontal pipe, with a series of orifices in one of the long sides of the room. At the bottom of this flue should be placed either a little grate or three or four gas-burners, each consuming about four cubic feet an hour, in order to keep up the draught when the external temperature is too high for natural ventilation to be effective. The use of gas is in most cases of this kind more convenient than a coal-fire.

On the side opposite to that by which the foul air is carried off, a number of ventilators should be put in place of the upper panes of the windows, and arranged so as to be opened more or less as needed, in order to admit the fresh air as near as possible to the ceiling. By increasing and suitably arranging these openings, the injurious effects from the entrance of cold air will be avoided.

Arrangements of this kind have been recently adopted in the school at Saint Martin's Market, kept by the Christian Brothers, where there are about 100 scholars in the drawing-room every evening, light being furnished by a great many gas-burners. Simple wooden pipes carried up to the roof, and the employment of a few gas-burners, prove sufficient to carry off the foul air and gas, and indirectly to draw in fresh air

through the ventilators placed on the opposite side to that by which the foul air is removed.

These means are far from being perfect, but their employment in school-buildings already built is almost always easy and inexpensive.

LYCEUMS AND COLLEGES.

66. In these institutions, where it is of the greatest importance to secure the change and purity of the air so as to promote the physical development of the youth, it is well to provide for this renewal at the rate of 500 cubic feet of air an hour for every child under 12 or 14 years, and 900 cubic feet for every person 15 years old or older.

The class and study rooms having to be warmed and ventilated constantly during the day, and the sleeping-rooms during the night, it is best to make use of such forms of heating and ventilating apparatus as include all the rooms of the same building. Those employing hot water should always be preferred, notwithstanding their greater first cost, because that is largely compensated for by their regularity of operation, and also by their economy of fuel.

Cast-iron stoves, too often used in these establishments, are extremely injurious, not only because they heat too irregularly, and often to excess, but also because the iron, a porous metal, produces a noticeable and dangerous alteration of the air.

67. Application made at the Toulon Lyceum.-M. Laval, one of the most skillful of French architects, and one who has for several years past been specially occupied with questions relating to the healthfulness of habitations, has made a very happy application of the principles just mentioned in the new lyceum at Toulon, which he designed. Some details in regard to it will prove of interest, since they will serve both as an exemplification of the rules and as a model to be followed in similar circumstances.

Fig. 16.

In this establishment, there is a main court-yard, giving access to all the rooms, (Fig. 16.) This communicates right and left, by means of passages, with the halls, studies, and class-rooms of the first and second divisions. At the rear, in a separate building, are placed the natural-history collections and the physical apparatus. Behind this building is the hospital-court,

around which are, on the ground-floor, the dining-rooms and the kitchen, and, on the second floor, the infirmary with its bed-rooms.

The lyceum will accommodate 300 boarding scholars, occupying during the day six study-rooms and at night ten bed-rooms. There are also twenty-two class-rooms, each intended for forty scholars on an average, which should be ventilated at the same time as the study-rooms. All

the class-rooms and studies on one side of the staircase have together a content of 42,000 cubic feet, which is to be ventilated by one apparatus; and the two sleeping-apartments placed above these rooms have each a capacity of 37,000 cubic feet, or together 74,000 cubic feet. The chimney and the ventilating-apparatus, which will be described hereafter, then serve during the day to ventilate the recitationrooms, containing 42,000 cubic feet of air, and during the night the bedrooms, containing 74,000 cubic feet.

The class-rooms and study-rooms in each division are placed on the ground-floor of large buildings, of which the second floor contains the corresponding bed-chambers. A fine staircase, placed near the middle of each wing, gives access to the rooms. Fig. 17 shows the general

Fig. 17.

arrangement of the ground-floor of one of the four similar buildings. The climate of Toulon is so mild that no arrangements for heating had to be provided, but ventilation appeared still more necessary under the southern sun than almost anywhere else.

M. Laval took as a basis for the calculations and the dimensions he adopted the renewal of a volume of air of 900 cubic feet an hour to each person, which seems amply sufficient.

The ventilating-flues were made in the thickness of the walls of the rooms on the ground-floor and the sleeping-rooms; their number as well as their areas were calculated by allowing a velocity of about 28 inches a second to the air passing into them, (Fig. 18.)

Fig. 18.

The general system adopted is that of a descending draught, and the ventilation is confined during the day to the lower rooms and at night to the sleeping-rooms.

The descending pipes, which receive the foul air at each side of the front rooms, unite under the floor in two central collecting-pipes, placed right and left of the staircase, each terminating in a ventilating-chimney, of which there is one on each side of the staircase.

Each story has its ventilating-pipes and its special collecting-pipes,

Fig. 19.

and the two collectors on one side are placed one over the other, as seen on the plan of the basement, (Fig. 19.) As the ventilation of the two stories alternates day and night, a valve placed in the chimney at the mouth of the collectors allows that for the sleeping-rooms to be closed during the day, and that for the class-rooms at night.

A coke-stove, only filled every twelve hours, the draught of which can be regulated at will, is placed at the bottom of each chimney, to conrol the ventilating-current.

Such are the simple and inexpensive arrangements adopted for the four buildings containing the study-rooms, class-rooms, and dormitories.

The building containing the dining-rooms and the infirmary is venti lated in a similar way; but for them M. Laval has skillfully made use of the waste heat from the cooking-range, in which fire is kept most of the day.

In the dining-rooms, the tables are arranged on the side opposite to an outer wall, pierced with many windows, which admit light and air from the infirmary-court. The ventilating-openings are arranged in the face of the opposite wall in the space between the tables. The vertical flues lead into collecting-pipes, which carry the foul air to the bottom of the kitchen-chimney; and this is always warm enough to produce a sufficiently powerful draught.

For the infirmary, situated on the second floor, the arrangements are similar; and as the dining-rooms only need to be ventilated at certain hours, the heat of the kitchen-range and that of the fires used in preparing decoctions and poultices, not only serve without expense to carry off the foul air, but also to heat the baths required in the establishment. Introduction of fresh air.-The mildness of the climate of Toulon allowing, as has been said, artificial heat to be dispensed with, the introduction of fresh air does not present any difficulty, and no precaution is necessary, except to prevent the draught from becoming unpleasant. M. Laval has provided for that by placing ventilators in place of the upper panes in the window to throw the air toward the ceiling. A valve allows the amount of opening to be regulated when the force of the draught renders it necessary.

In the sleeping-rooms, he has added convenient arrangements for the renewal of the air during the night; the opening of little doors placed under the window-ledge allowing the air to flow out at the floor-level and under the beds in order better to purify the room.