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100 so green a color that the wall beneath changes perceptibly in tone. The white cathedral glass is thinner than most and perhaps for that reason gives the whitest test; it conforms to two and four also, but is not very successful in three. The rippled glass which has been used in the Metropolitan fulfils all four requirements well. It is subject to one disadvantage, however, in that it is made only in small sizes.

The danger of breaking a pane of glass is great, especially during cleaning, but there is no wired glass on the market sufficiently clear to be used in skylights. Wire netting stretched under the glass serves the same purpose.

The color can be seen in a small sample on the cut edges. All thick glass shows green when cut, but the shade and intensity of the color vary with the kind of glass. On this subject see: Charles L. Norton, A New Era in Interior Lighting. Technology Quarterly, vol. XIV, No. i, page 33. E. J. Edwards, The Lighting of Rooms Through Translucent Glass Ceilings, paper read at the eighth annual convention of the Illuminating Engineering Society, Cleveland, Ohio. September, 1914.