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_.