as can be inferred from the above discussion, that it necessitated dropping the tops of the windows too far below the ceiling line.

As mentioned elsewhere, no pupils should be seated at a greater distance from the windows than that equal to twice the height of the tops of the windows from the floor. And this, too, only on the condition of the proper amount of window surface. Where it is impossible to get sufficient light from ordinary windows, due to errors in plans or to conditions over which builders have no control, prismatic or ribbed glass may occasionally be used with profit. As the result of a series of tests made by Professor Norton, of the Massachusetts Institute of Technology, it was found that by the use of this ribbed glass, set in the upper parts of windows, the illumination on dark days could be increased under certain conditions from 40 to 50 per cent.

The proper arrangement of shades for the windows is not an easy matter. Blinds ought not to be used at all, for the reasons spoken of above, and for the further reason that they are far more expensive than common roller shades, and frequently become hard to manage.

The best arrangement of roller shades which has been devised consists in using two separate sets of shades for each window, both fastened at about two-fifths of the height of the window, the upper one to pull up and the other to pull down. Care must be taken to place them in such a way that they will not rub together when both are rolled up, nor leave a chink through which a stream of light may pass when both are unrolled. Special brackets have been devised for these fastenings and are now on the market. The shades should be wide enough to cover the window and extend over each side of the window frame, to prevent rays of light from passing the sides. This last precaution will save much annoyance later.

There is on the market now a type of shade which folds rather than rolls; fastens at the center above, and can be adjusted to cut out the light from any part of the window. It requires more care in handling than the roll type of shade, but if teachers will learn to use it and take the time to adjust it carefully, it will meet the needs better than any single shade.

There has been a great deal said about the proper color of the shades, and many experiments have been made to find the color and tint most satisfactory to the eyes of children, which will at the same time serve to prevent the entrance of dazzling light. Some have advised the use of an opaque dark green shade below and a translucent lighter green one above. This arrangement, however, can be satisfactorily only when the shade used above is sufficiently opaque and sufficiently dark to avoid that peculiar greenish light which makes

2. BOX STOVES.

The box stove came next with its greater efficiency and economy. It heated the room but afforded no effective means of equalizing the temperature in the various parts of the room. When situated in the center of the room it was in the way, and because of the fact that it was out of the question for a pupil to sit near it when it was heated sufficiently to meet the demands of those occupying benches next the walls much of the best space of the schoolroom was wasted. If placed near the end or side of the room, it was ineffective for the room as a whole. The roastings to which the school boys of a generation ago were subjected remain yet as vivid impressions. Fortunately, vigorous outdoor employments and sports, together with short school terms, minimized the dangers. In early days the school buildings were often built in such a way that the wind swept under the floor at will. Double floors with deadening felt were not known, or if they were, knowledge in this case at least had no relation to virtue. Single floors with open cracks were the rule. The walls were made of studding, covered on the outside with one thickness of clapboards put on shingle fashion, and on the inside with wide boards tongued and grooved. Shrinkage was ample and hence the stove must be kept red hot in cold weather. Log houses well chinked were in some respects much better, but small and awkwardly fitting windows in these generally evened up the difficulties.

The great majority of the country schools in parts of our country are yet in the box-stove era, but the buildings are being more carefully made, and hence the children are somewhat better protected from the cold.

3. JACKETED STOVES.

The jacketed stove is the next step in the evolution of heating small school buildings. A jacketed stove, as its name indicates, is a stove surrounded with a casing or jacket, between which jacket and the stove there is left an air space connected directly by means of one or two ducts with the air outside. These ducts permit the cold fresh air from the outside to come in contact with the stove and when it is warmed to rise directly into the schoolroom. The jacket when properly fitted serves to keep this fresh air close enough to the stove to warm it, and at the same time to deliver it into the room well above the breathing line. It is well to provide the freshair inlets with dampers to be used during troublesome winds.

In recent years a great many varieties of jacketed stoves have been put upon the market, all of them using of course the same principle of heating fresh air and distributing it through the room and at the same time creating a circulation by exhausting the air in some

fashion near the stove. They can be set in the corners of the room, draw the fresh air directly from without, and heat and deliver it to the classrooms directly. At one time it was thought of great importance to have an exit flue or a pipe attached to the stove and extend nearly to the floor. The theory was that as the warm expanded air swept upward and outward to the various parts of the room that the air would leave the room through this flue and thereby create considerable circulation. This theory works in part, but is not nearly so effective as many imagine. Much of the incoming air goes out around windows and doors and various openings in the wall, especially those higher up in the room. The heavier air lies nearer the floor and hence is not inclined to be drawn readily through the exit flue. In the former edition of this bulletin more stress was laid on the necessity of providing exit flues than now seems justifiable. The friction in these flues is often so great and their lack of sufficient draft so correspondingly poor, that a smaller amount of impure air is exhausted than was thought to be the case. I do not mean by this discussion to suggest elimination of these exits from jacketed stoves, but simply to warn schoolmen against believing that the jacketed stove will ventilate a schoolroom. It will aid much in very cold weather, but in mild weather it is of very little use in supplying fresh air to classrooms. The fact is a jacketed stove can not be trusted to ventilate satisfactorily at any time and not even passably, save in cold weather, but is of great service in equalizing the temperature in various parts of a classroom. But it is the best method of heating where a central system can not be installed. Every country school, or for that matter village school, not supplied with a central heating plant should be supplied with jacketed stoves.

4. HOT-AIR FURNACES.

Hot-air furnaces are so well known that any extended description of them is unnecessary. Suffice it to say that the furnace of a hot-air heating system must be placed in a basement or at least in a room lower than the space to be heated unless mechanical contrivances are utilized to drive the heated air into the building. Like any central heating system it has the great advantage of keeping fuel and other débris out of classrooms and confining the fire hazard to some central location where it can be guarded much more safely. Naturally the distribution of ducts leading to various rooms to be heated and the location of the furnaces are of prime importance. Very frequently disastrous mistakes are made in locating and properly proportioning the system of ducts to the various rooms. A hot-air furnace gives off heat quickly, and likewise, unless care

fully handled, loses its heat speedily and hence is likely to cause a good deal of fluctuation in temperature in the classrooms. There are some serious objection in addition to the foregoing which may be briefly stated as follows:

There is danger that the gases produced through combustion, especially of coal or oil, will leak through the joints in the furnace and enter the air passing into the schoolrooms. The danger is especially marked when through carelessness of the janitor or the person who tends the fires the furnaces are overheated and then somewhat suddenly allowed to cool by opening the doors of the fire boxes. In cold weather, when it is necessary to heat the radiating surfaces very hot to supply enough heat in the rooms, the danger is more marked. It must ever be remembered that however tight the joints are made in the beginning, any furnace fire box is subject to great strain, through the expansions due to heating and the contractions due to cooling. These strains will in time open the joints and furnish opportunity for some of the carbon monoxide and sulphurous gases generated by a coal fire to escape into the air ascending to the rooms. The only remedy for such a defect is to make the heaters so large that it will be unnecessary to make them very hot to raise the amount of air needed to the temperature required. It is obvious, then, that an overworked furnace is the most dangerous furnace when leakage of gases is considered, and the most expensive in the cost of fuel and labor. The practical lesson to learn here is this: If a hot-air furnace is to be used for heating the air and delivering it to the schoolroom, it is essential to install one abundantly large, so as to heat all the air needed without the necessity of overheating the fire box. It is in no sense an exaggeration to assert that 75 per cent of the furnaces for heating schools which I have examined are too small for either safety, economy, or health.

In large buildings where this method is used it is good economy to have two or more furnaces in different parts of the basement and to adjust the fires accordingly. This plan of separate furnaces has the double advantage of preventing overheating and of making it much easier to introduce the air into the rooms without serious friction in the ducts and with a minimum loss of heat through radiation. For long air ducts, especially where there is much horizontal run, offer so much friction to the passage of the air through them and afford an opportunity for so much loss of heat that they are almost useless when depending on gravity for air movement; and even when a fan is used they are still ineffective.

When cold air comes in contact with overheated radiating surfaces it becomes dry and, as it were, parched. Such air is in effect desert air, and when introduced into a schoolroom will rapidly absorb 93146°-25-5

moisture from the skin and especially from the lining membranes of the eyes and air passages. Such continual absorption renders the skin, and more specially the mucous membranes of the eyes, nose, throat, and trachea, dry and harsh. Such a condition, as everyone ought to know, offers ideal opportunity for pathogenic germs to lay hold of these delicate tissues and penetrate into their crypts. When the lining membranes of the air passages are coated with their normal moisture or mucus it not only serves to prevent these germs from so readily reaching the tissues but it also catches dust particles and thereby prevents them from being drawn into the lungs. After a ride in dust and smoke the condition of the lining membranes of the nostrils will bear witness to this fact. Besides, it seems quite probable, if not certain, that these mucous exudations may have germicidal properties which have hitherto escaped scientific detection.

All hot-air furnaces should be supplied with some means of moistening the air before it is introduced into the schoolroom. Especially is this necessary in cold climates where the amount of moisture mixed with the air is necessarily small and where its temperature must be raised 40° or 50° F. The expansion of the air thus taking place will further reduce the percentage of saturation very greatly, and serious and annoying dryness will result; and then we have a desert atmosphere in the schoolroom. The problem of heating is intimately connected with the problem of securing satisfactory humidity in the air. Obviously, the supply of fresh air to the radiating surface of a hot-air furnace or, for that matter, to any heating surface used should enter through a clean passageway and from a point well above the ground. The walls of the passageway and the fresh-air chamber near the furnaces should be carefully constructed of glazed brick or lined with smooth, hard cement, in order that as little friction as possible will result as the air passes to the heating surfaces. The floors of these air passages should be cemented and kept scrupulously clean, for any dirt or dust that enters them will quickly find its way into the schoolrooms.

If the opening for the entrance of fresh air is placed 6 or 8 feet from the ground there is much less likelihood that dust from the playground, the roadway, or street, or contaminated ground air will be drawn into the schoolrooms. This opening should be securely screened so as to keep out the larger particles floating in the air during high winds, and to prevent anything from being thrown into it, such as apple cores, orange peels, or anything else that would vitiate the air or litter the floor. These passages must be carefully closed below and as far as possible made air-tight so that foul air may not be drawn into them from the basement. The location of the opening to receive the ingoing fresh air is a matter of much importance on