Limestone walls conduct more heat in and out than an equal thickness of glass, bricks, plastering, and wainscoting. The porosity of the building material determines the interchange of the air through the walls, and it affects the temperature of the rooms. If there is water in the pores of the walls heat is conducted rapidly, but air is not permitted to pass. Brick as a building material has many disadvantages, but on the whole it is best for schools, and it resists fire better than most stones. The harder the brick the better it is—vitrified brick is the best. Hard-pressed brick of a light colour makes an excellent outer wall-surface.

It is very doubtful that sewer gas escaping into a house will directly carry the micro-organisms of diseases like typhoid and diphtheria, but such gas is poisonous, depressant, and it renders the inmates of a house liable to disease; lessens their power of resistance. The typhoid bacillus and other bacteria can, of course, be carried into a cellar by the seeping in of drainage water. Infants kept in the upper story of a house in hot weather are more liable to intestinal diseases than are those that live on the lower floors, but here the weakening agent is heat. Tuberculosis, scrofula, rheumatism, neuralgias, bronchial, and kidney affections are made worse in damp houses.

The chief defects in plumbing and drainage are the following: (1) Earthen pipe drains become broken or their joints leak, and they saturate the ground under a house with sewage. (2) Tree roots break and clog drain pipes. (3) The pipes sometimes have not fall enough. (4) Drains without running traps admit sewer gas. (5) Rats burrow along a drain pipe from the sewer into the house and admit sewer gas. (6) When the soil pipe from a water-closet is exposed in cold weather it may freeze up or be clogged by urinary deposits. (7) Rats gnaw through lead pipes and joints. (8) Two or more closets or sinks with unventilated [{204}] traps on the same pipe will siphon back sewage. (9) Overflow pipes sometimes have no traps and they let in gas. (10) Ash pits near a house carry moisture to walls, (11) Cesspools leak through the soil.

In planning a school-building the classrooms and the study-halls are the first things to be considered. The classrooms should be oblong, with the aisles running lengthwise. Each child should have at the least 15 square feet of floor space and 200 cubic feet of air space. A room 30 by 25 feet with a ceiling 13 feet from the floor will serve for 48 pupils and no more. This is the best size for a room when blackboards and maps are used in teaching, because a larger room sets the children in the back seats too far away to see without eye-strain.

Dormitories should have at the least 300 cubic feet of air space for each child, and great care is to be taken in the ventilation. Children about 10 years of age require 11 hours of sleep; under 13 years, 10-1/2 hours; under 15 years, 10 hours; under 17 years, 9-1/2 hours; under 19 years, 9 hours. Do not make children get out of bed before seven o'clock in the morning; do not let them study before breakfast, and do not force them to work after half-past eight or nine o'clock at night until they are at the least 17 years of age. The hours for work should be:

Ages--From Hours of work a week
5 to 6 6
6 to 7 9
7 to 8 12
8 to 10 15
10 to 12 20
12 to 14 25
14 to 15 30
15 to 16 35
16 to 17 40
17 to 18 45
18 to 19 50

Work given for punishment must be included in these hours. No one, even an adult, should study for more than two hours at a time without an intermission for a few [{205}] minutes. In a boarding-school no one under any pretext, even on rainy days, should be permitted to study during recreation hours, and the deprivation of recreation to make up lessons is a relic of barbarism. If a teacher can not get class work done except by shutting up children during recreation hours, remove the teacher or expel the pupil.

The amount of glazed window surface admitting light to a classroom or study-hall should be from one-sixth to one-fourth the floor space of the room, and this must be increased if the light is obstructed by neighbouring houses or trees. The light is to be admitted on the left side of the pupils,—all other windows should be counted as ventilators only. Windows facing the children or the teacher are to be avoided. In rooms fourteen feet high a desk twenty-four feet from a window is insufficiently lighted. The larger the panes of glass the better, and the external appearance of windows is to be sacrificed to good lighting. If screens are used to protect the glass from stone-throwing, allowance is to be made for the light the screens cut off.

If a room can not have enough light from the left side alone, put the additional windows on the right so that their lower sills will be eight feet from the floor; and be careful in this case that the light from the right is not brighter than that from the left.

Windows should have as little space as possible between them to avoid alternate bands of shadow and light. Set them up as near the ceiling as possible, since the higher they are the better the illumination; and they should not be arched at the top. The lower window sills may be about four feet from the floor. When window shades are used to cut off direct sunlight, they should be somewhat darker in colour than the walls.