Mr. Atkinson proceeded to gather specimens of glass not only of common rough surface, but also in ribbed and prismatic forms. These he handed for examination and comparison to Professor Charles L. Norton of the Massachusetts Institute of Technology, Boston. His report says: “The hopelessness of trying to get something for nothing, that is, to get a sheet of window glass to throw into a room more light than fell upon it, appeared so plain to me that I made all my preparations to measure not a gain but a loss of light in using Mr. Atkinson’s samples. The results of the tests may be briefly stated: In a room thirty feet or more deep we may increase the light to from three to fifteen times its present effect by using ‘Factory Ribbed’ glass instead of plane glass in the upper sash. By using prisms we may, under certain conditions, increase the effective light to fifty times its present strength. The gain in effective light on substituting ribbed glass or prisms for plane glass is much greater when the sky-angle is small, as in the case of windows opening upon light shafts or narrow alleys. With the use of prisms a desk fifty feet from a window has been better lighted than when but twenty feet from the same window fitted with plane glass. . . . ‘Ribbed’ and ‘Maze’ glass are of very great value in softening the light, especially when windows are directly exposed to the sun, aside from their effectiveness in strengthening the light at distant points. With the ‘Maze’ glass the artist may have, in all weathers and in all directions, what is in effect a much-desired north light. The same glass provides the photographer with light as well diffused as when cloth screens or shades are employed and of much greater intensity.” Plate prism glass is now manufactured with its outer or street surface ground and polished like plate glass, with its prisms accurate and smooth. In dimensions which may reach fifty-four by sixty inches it affords surfaces easily kept clean, and transmitting much more light than glass held in frames of small divisions.