three inches from the copy-books; and a distorted position of the body is inevitably produced by, the faulty shape of the desks. These scholars, the teacher says, write about twenty minutes a day, and that cannot be long enough to inflict any permanent injury. But in another room they are adopting the "Quincy method," and the scholars write a good deal more; and in the upper classes they write long translations and compositions, and copy out lectures.

In another room may be seen a class of girls and boys of about fifteen or sixteen. They pass in file, and there is opportunity for seeing that not one in ten of the girls has an erect figure; many stoop painfully, and among forty whom the eye reaches, four or five appear to be deformed with lateral curvature of the spine. Here is a tall young woman, who sits, like others, with the upper part of her body across the desk in an attitude of fatigue. She is an overworked person, and the school is not wholly to blame for that. But the school may be responsible for the ill-shape of the back of her chair, which gives her no real support in sitting, and compels her to lean forward instead, to relieve a pain in her back.

Such facts as these will constantly meet the eye of one who visits our common schools and studies the health of their inmates. And is there not an inference from such facts? Are they, perhaps, of that class which imply a duty and a responsibility? Human life is the best of human possessions; and the best part of life is the hope that we are leaving behind us those who will be more able and worthy to enjoy it than we have been. These successors of ours are the children. Can any thing touch us more closely than the thought that there is a group of influences, manifold and wide-spread, which are constantly acting to lessen the worth of their young life?

This is a complex field of study, for it includes at one end the details of certain branches of physics and engineering, and extends on the other to questions regarding the powers of young minds, the means of developing without straining them, and the precautions against injury to the highest of the senses. However tempting this field, it is necessary here to limit our scope to the principles and details of what may be called "sanitation" in the most limited sense of the term. In other words, to attempt an answer to certain questions which are most frequently and properly addressed to a board of health, considered as a sanitary counsellor of the people. Such questions belong under the general headings of ventilating and heating; lighting, and the care of eye-sight; planning of school-houses; school desks and seats, and other topics which cannot be fully dwelt upon here.

This paper is meant to be of use to those most concerned with the details of daily school life, with whom the writer has been in frequent contact, and to whom he is happy to acknowledge an indebtedness for many valuable suggestions.

VENTILATION AND HEATING.

"How much?" and "How?" are the two great questions in ventilation.

Ventilation implies getting bad air out and pure air in. How much good air does one person need? Enough is needed so that a person coming in from the fresh air shall not notice closeness, or a smell of closeness. In a house permanently dwelt in, sixty cubic feet per minute, for each person; in a house occupied for short times and then aired out by sweeping draughts, thirty cubic feet per minute, or half a foot per second.*

If we wish to ascertain by calculation how much the ventilating arrangements of a given room are actually supplying, we had better limit the question at first to the point, how much air is drawn out or makes exit in each minute or second of time? Evidently, for each cubic foot of air taken out another foot must come in. It will be right to ask afterward whence the new supply comes, and what its degree of purity is. But in our climate rooms cannot be ventilated without flues, and if the flues are adequate to their duty all the air that leaves the room will leave through them. If the flues are weak and insufficient we may find, even in winter, that hot air will go out at an open window; but if they are large and powerful, we can open windows so that the air will come in forcibly.

Few people are aware how small a quantity of air is actually drawn out of apartments by ordinary flues for ventilation. By "ordinary" I mean the old-fashioned sort, of the size of one or two bricks, 4x8 inches, or something about that, with a close grating called a register to obstruct the current at the bottom, a sharp angle at the foot, the inside roughened by protruding mortar and with only an accidental opportunity of getting warmed by contact with a smoke-stack. You stand

The amount of fresh air required is the amount which is needed in order to dilate the impure air to a certain standard of relative purity. All good air contains a small proportion (4–10000) of carbonic acid gas; when human breath is added, the amount is increased. It is found by experience that when this increase brings the total amount to beyond 6-10000, the air begins to smell close. A person may, therefore, add two parts of carbonic acid to 10,000 of air before it becomes objectionable. If he should breathe out two feet of the poisonous gas in an hour he would affect 10,000 feet of air to this extent; but as the real amount expired in an hour is about one-third of two feet, he uses and renders unfit for use onethird of 10,000 feet, or (more exactly) 3,500 cubic feet of fresh air per hour.

in front of it with a light pocket handkerchief; the cloth is gently drawn toward the opening; it deviates a couple of inches; you say "it draws," and are satisfied. "The thing is working." Probably, in such a case, the rate at which the current moves is something like a foot per second. The flue is drawing out a quarter or a half of a cubic foot of air per second- enough, perhaps, for one person's requirements. A large schoolroom may often be seen provided with half a dozen or more of just such ventilating flues, which are considered to be "the correct thing," and are pointed out to the visitor as the evidence of good ventilation in the house. Evidently the question of "How much?" is of leading importance in some other matters than those of finance and trade.

It is strongly to be recommended that school authorities should take steps for ascertaining the real working capacity of the flues in the school-houses, for the degree of deficiency can never be known in any other way. The anemometer will give a pretty faithful statement of the current actually passing the flues. Analysis for carbonic acid in the air of the room will give an excellent test. Nor ought we to pass without mention the useful but too often uneducated sense of smell; it furnishes data which make the foundation of all our mathematical calculations, and is by itself a faithful guide for a short time.

A ventilating flue must draw, or it is worthless. This quality, which forms its sole merit, is aided by several other points.

1. It should be as straight as possible from beginning to end. Curves and angles are very great obstructions.

2. It should not, as a rule, be horizontal, or descending in any part. There are special exceptions to be noted hereafter.

3. It should be continuous from the beginning to where it discharges out of doors. A flue that ends in an attic has less carrying force than one that goes up through the roof. The air comes up with a rush, and is dispersed in the air of the attic; the rush, the momentum, which it brings with it is lost in the space. True, the air will get out by an Emerson ventilator at the ridge-pole, if there is one, but the conditions for successful working are best attained by a continuous column.

A tight box lined with tin may properly be used to collect the flues and discharge their collective contents by an opening, as in Fig. 1. 4. It should be smooth internally. A tin pipe is as good as any, and has the advantage of not parting with heat so quickly as dark or slightly roughened metals will. If a brick flue is used it should be larger than the dimensions named above, and should be plastered smooth inside. The hollow spaces in walls should not be relied on to do the work of flues. The width is very small, and the friction against the bricks or lathing is enormous.

5. It should be so protected as to lose no heat. A tin flue passing through a cold entry should be boxed with wood. It should not have a very great distance to traverse in the open air, if of metal. There is, therefore, a certain advantage in compelling tubes to converge inside of the attic, as in Fig. 1, instead of passing up straight through the roof, as in Fig. 2.

6. It should be so protected that the rain will not beat in or the wind blow down. Certain caps will accomplish this object satisfactorily.

FIG. 1.

There are other caps which increase the upward draught when the wind is blowing upon them, but their action is uncertain, and they may sometimes check the upward current instead of assisting it. The

outlet should not be a narrow one, barely equalling the capacity of the flue, and compelling the current to twist and turn in making its exit.

7. The flue must be devoted to the uses of a single room. If it opens to rooms on successive stories it often serves as a passage from one story to the next above, especially when the flue is not warmed. The heated flue, on the other hand, when drawing from different stories at once, has a much less powerful action upon the upper story.

FIG. 2.

8. The flue should be warm; at least it must be as warm or warmer than the outer air, or else the current will be inverted.

Flues ought not to be placed in outer walls. Much heat is lost and the opportunity for heating by contact with the chimney is sometimes omitted. An air-space is sometimes employed as a defense. When, for instance, the triangular brick flue is placed in the corner of a room (which is a good arrangement for saving space), the wall should be double on the outside.

The subject of applying warmth to flues is a somewhat extensive one, but a few methods ought to be mentioned.

(a) A brick triple-shaft with the central part devoted to the smoke. from the furnace and the two side-flues for ventilators.