Methods of Ventilation. Fortunately, as often happens, the simplest and most natural method of ventilation is the best one. Open the windows, and let the fresh air pour in. If there be any room which hasn't windows enough in it to ventilate it properly, it is unfit for human occupation, and is seldom properly lighted. Most elaborate and ingenious systems of ventilation have been devised and put into our larger houses, and public buildings like libraries, court-houses, capitols, and schools. Some of them drive the air into each room by means of a powerful steam, or electric, fan in the basement; others suck the used-up air out of the upper part of each room, thus creating an area of low pressure, to fill which the fresh air rushes in through air-tubes or around doors and windows. They have elaborate methods of warming, filtering, and washing the air they distribute. Some work fairly well, some don't; but they all have one common defect--that what they pump into the rooms is not _fresh_ air, though it may conform to all the chemical tests for that article. "The proof of the pudding is in the eating," and fresh air is air that will make those who breathe it _feel_ fresh, which the cooked and strained product of these artificial ventilating systems seldom does. [Illustration: THE "DARK ROOM" DANGER OF THE TENEMENTS The rooms "ventilate" from one to another; bedroom, dining-room, and kitchen being practically one room, with only one window opening to the _outer air_. Most of the old small tenements were built on this plan and are accountable for much of the lung disease in cities to-day.] If they could be combined with the natural, window system of ventilation, they would be less objectionable; but the first demand of nearly all of them is that the windows must be kept shut for fear of breaking the circuit of their circulation. Any system of ventilation, or anything else, that insists on all windows being kept shut is radically wrong. It is only fair to say, however, that most of these systems of ventilation attempt the impossible, as well as the undesirable thing of keeping people shut up too long. No room can be, or ought to be, ventilated so that its occupants can stay in it all day long without discomfort. In ventilating, we ought to _ventilate the people in the room_, as well as the room itself. This can only be done successfully by turning the people out of doors, at least every two or three hours if grown-ups, and every hour or so if children. That is what school recesses are for, and they might well be longer and more frequent. [Illustration: VENTILATING THE PUPILS, AS WELL AS THE CLASSROOM] The first and chief thing necessary for the good ventilation of houses and schools is plenty of windows, which are also needed to give proper light for working purposes, and to let in the only ever-victorious enemy of germs and disease--sunlight.