Page:The museum, (Jackson, Marget Talbot, 1917).djvu/93

Rh a much greater amount of ventilation through the skylight and the fact that it has a solid roof makes both the glare and the heat admitted less intense.

In the case of rooms which are by nature dark, where the diffusion of light is poor, something may be done by the use of prismatic glass, although its makers no longer claim for it the tremendous power it was thought to have when first discovered. One of the most interesting uses of prism glass may be seen in the Fogg Art Museum at Cambridge, Mass. There it is used as a supplement to the glass in the ceiling placed at an angle to it and diffusing the light in certain sections of the room. The problem there was that the light was too great in the front of the room and too little in the back. The diffusing glass placed at an angle has corrected this, so that now the light is evenly distributed throughout. Intensity of light is one of the most difficult things to gauge with the naked eye and a prism glass will invariably give the effect of darkening the room when used in side-light windows, from the fact that the observer cannot look through it. It has been claimed that the intensity of the light admitted through prism glass is the same as that admitted through ordinary glass, but the diffusion is much greater. Thus, a room opening on a small