The Investigation of the Colour and Intensity of Daylight and the Optical Properties of Various Kinds of Glass

Abstract

In order to obtain the necessary data concerning the colour and the intensity of daylight at various times of the day and for various days in the year the following investigations were carried out: for two years, daily, at about 9, 12, 14 and 17 o’clock the brightness of a horizontal white surface exposed to the radiation of the entire hemisphere of the sky was measured as a function of the wavelength. The times, mentioned, were chosen so as to cover the usual visiting hours of a picture gallery. As for using the light from the entire hemipshere, considering that this investigation was begun on behalf of the planned construction of the new Municipal Museum at the Hague of which the roof, owing, to its favourable situation, receives the light from the whole hemisphere of the sky, we were bound to carry out our measurings under similar conditions.