Page:Popular Science Monthly Volume 71.djvu/312

306 figures are the average for the school days of 22 months in one city, and although observations for a longer period and in other cities might change the results somewhat, it is safe to assume that our figures are not far from the actual conditions in a majority of our school rooms in the United States. In general a room which is barely adequately lighted at 12:30 will be 33 per cent, under-illuminated at 9 o'clock, and at 4 o'clock its illumination will be but 27 per cent, of the necessary amount.

Our difficulties are further complicated by the fact that the variations in illumination of daylight are as great between the months of the school year as between the hours of the school day. The illumination is best in the months of June, July, August and September. Then follows in order May, April, March, October, February, November, January and lastly December. Comparing the illumination of the four bright months (June, July, August and September) with the four dark months (November, December, January and February) we find that for the 22 months observed the illumination of the dark months is but 28 per cent, of that of the bright ones. This figure is found by averaging the three daily readings for each day for all the months concerned. December, the darkest month has but 18 per cent, as great illumination as June, the brightest month.

When to these variations as between months or seasons we add the variations between mid-day and morning and evening, the results are most astounding. The light at noonday in June averages almost ten-fold as much as that at 9 in December. If it is injurious to read with a light less than one or more than ten-candle power, a schoolroom that furnishes this maximum in June will be reduced to the minimum in December mornings and evenings on average days. Such deviations in the external source of light put most restricting conditions upon school architecture. How have we met the conditions and how might we construct our schoolrooms to meet the situation satisfactorily?

In our climate it is almost impossible to over-light a school room if the two following conditions are observed: (1) Never allow the direct rays of the sun to fall upon any surface within the field of vision of any pupil. (2) Avoid all glossy or shiny surfaces which reflect the light directly into the eyes of the pupils. A dead white surface is not injurious, while a darker surface may be shiny and hence injurious.

For securing adequate light the following rules are important: (1) The window space should be as much as one fifth of the total floor space, and the height of the window two thirds of the width of the room. (2) The walls, ceiling, woodwork, furniture, etc., should be a color which reflects a large amount of well-diffused light. Perhaps