Very Important to Read
Report of a leading authority upon the diffusion of light
through windows, as obtained by Maze, Colonial, Florentine and
Ribbed Glass.
THE use of glass in windows for the purpose of admitting light has
been common for many years; but it is only within a few years that
it has been deemed possible to give to the window glass a further
use, that of so rearranging the light as to greatly increase its
effectiveness. For twenty years or more rough plate glass and ground
glass have been in use where it was desired to have a window which
should be an obstruction to vision without materially diminishing
the light. Deck-lights, used in ships for thirty years or more,
have diffused or deflected the light to a certain extent.
In 1883 and 1884 examination of several
types of commercial window glass was made by Mr. Edward Atkinson, who
was apparently the first to recognize the immense gain in effective
light in rooms when lighted by windows which were roughened so that
the incident skylight or sunlight did not pass directly through
them, but was diffused in directions in which it otherwise did
not go. In the summer of 1894 Mr. Atkinson laid before me the
problem, requesting an examination of some dozen or more different
kinds of glass. 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 my tests at that
time showed how real was the gain in the amount of effective light
in small rooms when glazed with a roughened or corrugated glass.
The finely corrugated or ribbed glass, described more fully later,
was found to give the greatest increase, and has since been widely
used under the name of Ribbed
glass. Just as I was completing
my tests the now common prismatic glass began to be put upon the
market, and I tested it, finding it slightly less effective as a
diffusing medium than the Ribbed
glass. An examination of
the prisms then used and those now furnished by the company shows
a considerable gain in efficiency in the newer ones.
The results of the tests on a score or
more of different glasses may be stated briefly as follows:
We may increase the light in a
room thirty feet or more deep to - from three to fifteen times
its present effect by using Ribbed
glass instead of plain
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 plain glass is much greater when the
sky-angle is small, as in
