Whoever plans a house with a view to economy must arrange rooms around a central chimney, and avoid all projecting appendages. Dormer-windows are far more expensive than common ones, and are less pleasant. Every addition projecting from a main building greatly increases expense of building, and still more of warming and ventilating. It should be introduced, as one school exercise in every female seminary, to plan houses with reference to economy of time, labor, and expense, and also with reference to good architectural taste; and the teacher should be qualified to point out faults and give the instruction needed to prevent such mistakes in practical life. Every girl should be trained to be “a wise woman” that “buildeth her house” aright. There is but one mode of ventilation yet tried that will, at all seasons of the year and all hours of the day and night, secure pure air without dangerous draughts, and that is by an exhausting warm-air flue. This is always secured by an open fire-place, so long as its chimney is kept warm by any fire. And in many cases, a fire-place with a flue of a certain dimension and height will secure good ventilation, _except_ when the air without and within is at the same temperature. When no exhausting warm-air flue can be used, the opening of doors and windows is the only resort. Every sleeping-room _without a fire-place that draws smoke well_ should have a window raised at the bottom or sunk at the top at least an inch, with an inclined shelf outside or in, to keep out rain, and then it is properly ventilated, provided the air outside is colder than the inside air—but not otherwise. Or a door should be kept opened into a hall with an open window. Let the bed-clothing be increased, so as to keep warm in bed, and protect the head also, and then the more air comes into a sleeping-room the better for health. In reference to the warming of rooms and houses already built, there is no doubt that stoves are the most economical mode, as they radiate heat and also warm by convection. The grand objection to their use is the difficulty of securing proper ventilation. If a room is well warmed by a stove, and then several small openings made for the entrance of a good supply of outdoor air, and by a mode that will prevent dangerous draughts, all is right as to pure air. But in this case the feet are always on cold floors, surrounded by the coldest air, while the head is in air of much higher temperature. The writer believes that ere long the common mode of warming by furnaces will be banished as most pernicious to health, and constant sources of discomfort and economic waste. The reasons for this demand reference to some of the principles of pneumatics.