Trouble has always been found in regulating the supply of warmed air obtained by the indirect system, owing to the inability to control the heating surfaces. This may be obviated by enclosing the heating surfaces for each room in separate cases or jackets. These may be subdivided into five sections (see Fig. 15), so arranged that any number of the sections, or all of them may be used at discretion, thus graduating the heat to the condition of the weather. Thus, while

the supply of air remains the same, the degree to which it is heated is changed by the opening or closing of a valve.

A committee to whom was referred plans from which to select models for school buildings in the city of New York, made their selection, awarded the prizes according to the conditions of the prize giver, and then declared that none of the plans fulfilled the requirements of a sanitary school building.

The committee says: "A school building should possess the following qualifications when built in a city:

"1. It should be freely exposed to air and light, and should be not less than sixty feet distant from any opposite building.

"2. Not more than three floors should be occupied for class

rooms.

"3. In each class-room not less than fifteen square feet of floor area should be allotted to each pupil.

"4. In each class-room the window space should be not less than one fourth the floor space, and the distance of the desk most remote from the windows should not be more than one and one half times the height of the top of the windows from the floor.

"5. The height of a class-room should never exceed fourteen feet. "6. Ventilation should be such as to provide for each person in a class-room not less than thirty cubic feet of fresh air per minute, which amount must be thoroughly distributed without creating unpleasant drafts, causing any two parts of the room to differ in temperature more than 2° F., or the maximum temperature to exceed 70° F. This means that for a class-room to contain fifty-six pupils twenty-eight cubic feet of air per second should be constantly furnished, distributed, and removed during the school season. The velocity of incoming air should not exceed two feet per second at any point where it is likely to strike on the person.

"7. The heating of fresh air should be effected either by hot water or low pressure steam.

"8. The fresh air should be introduced near the windows; the foul air should be removed by flues in the opposite wall.

"9. The building not occupy more than one half the lot." This committee was composed of George R. Post, architect, New York; John S. Billings, Surgeon United States Army, and Vice-president of the National Board of Health; Hon. John D. Philbrick, United States Commissioner of Education at Paris and Vienna Ex

position; Wm. R. Ware, Professor of Architecture, Massachusetts, Institute of Technology; certainly men of authority and capability.

It would be wise to heed their advice and provide school-houses with sufficient light and ventilation, rather than turn loose crammed, near-sighted, round-shouldered boys and girls, with no health or disposition to work.

At the Centennial Exhibition at Philadelphia was shown a "model school-house," which had been approved and adopted by the government of Belgium. It received marked attention from those interested in educational subjects, and I therefore present the methods provided for ventilation:

1. The surbase was set off from the wall about four inches all around the room, thus forming an air space which was covered with perforated zinc. Several openings about eight inches square were made from this space to the outside. These openings were provided with hinged covers, to be opened or closed at pleasure; the air enters these openings, strikes the surbase, and is reflected upward into the room through the perforated zinc.

2. The lower sash of the room was fixed; the upper sash was hung on hinges at the bottom, and arranged so as to drop inward at an angle of thirty degrees or less, at will. The air entering the room strikes this inclined sash and is reflected upward to the ceiling, thus preventing direct draft upon pupils.

3. The stove received the air necessary to support the combustion of fuel, through openings in the floor.

4. The foul air was carried off through registers in each corner of the room, connected with flues under the floor, each flue forming a junction under the stove and connecting with a single flue in the stove, which passed through the roof. This flue was placed alongside the hot air flue in the stove, which created a heat and drew the foul air upward. A space was made around the ceiling of each room similar to that below at the surbase, and covered with perforated zinc. This space communicated with the outside air by pipes at each corner, eight inches in diameter, capped with an elbow and vane so arranged that the mouth of the cowl would be turned from the wind. This would cause a draft which would draw the foul air from the upper part of the room.

These plans of ventilation apply to large school-buildings, usually found built in cities and large towns. The large majority of our

school-buildings are of one story and heated by a stove.

To prop

erly ventilate such is a difficult matter, yet much may be done to secure good ventilation in such buildings. A. C. Martin, an architect of Massachusetts* has devised a plan which has been improved by Dr. Kedzie, and is shown in the diagrams Figs. 16-17.

The air to supply the lower room enters by the air pipe marked a, Fig. 16-17, passing beneath the floor and opening under the stove, b, around which is a galvanized iron jacket entirely surrounding the stove, (recessed for the stove door) and rising up as high as the top of the stove. The space between this jacket and the stove is one foot on all sides. The cold air as it enters is thus warmed by the stove before reaching the inhabited part of the room. The scholars sitting near the stove are screened from the excessive heat of the stove by this jacket.

The foul air is drawn off by the foul air ducts, f. f. f. f., these ducts being formed by the spaces between the joists which run lengthwise with the body of the house, while the joists in the vestibule run at right angles to these. The direction of the foul air is indicated by the arrows at the floor level. The foul-air flues all terminate in the front half of the ventilating shaft, d.

The straight arrows in the vestibule show the direction of ascent. up the stairs.

In the vertical section, Fig. 17, the letters have the same uses as in the ground plan. As it is essential that the ventilating shaft should be carried up some distance above the ridge of the roof, and as there is not room on the page to carry the shaft to the required height, and to represent the cowl on the top, the roof is cut away in the plate, and a break in the shaft indicates the incomplete extension of the shaft.

The position of the stove in the upper room is not indicated, but it has the same position, and is supplied with air in the same manner as the stove in the lower room.

The foul air of the upper room is drawn off by foul air-ducts exactly corresponding with those in the lower room, except that they all enter the compartment c. in the ventilating shaft. For successful ventilation it is essential that the foul air of each room shall enter a separate compartment in the ventilating shaft, and not one common shaft. These separate compartments are secured by having vertical

*Mass. Report of State Board of Health.