The herald., 1896-07-05
RIBBED WINDOW GLASS POPU-
LAR,
Supplies More Light Than the Plain Ar.
ticle Without Increase Of Heat.

ticle Without Increase Of Heat.
The advantages and disadvantages
arising from the substitution of ribbed
glass for plain glass in factory windows
were recently investigated for the Bos-
ton Manufacturers Mutual Fire Insur-
ance Company, by Charles l.. Norton Of
the Massachusetts Institute of Technol-
ogy. Mr.. Norton points out that in both
fair and cloudy weather the general re-
sultant direction of light entering through
window having ordinary glass is down.
ward at an angle of about 40 or 80 de-
grees. The brightest portion of the room
is, therefore, the floor in front of the win
dow. AS floor is not, as rule, good
rejecting surface, a large amount Of light
is absorbed there and lost. Whatever
light is reflected goes upward and back
ward toward the ceiling, and what light
| falls on the wall spaces between the
| windows must, therefore, be mainly light
| which is diffusely reflected from the
floor and objects upon 1t. Early in the
| morning and toward evening the angle
| of the incident light with the horizon
| tai is less. and the light. therefore, neps-
| trates further into the room, but the walD
| spaces between windows gain but little
| by this greater oblquity. If panes Of
| ribbed glass be substituted for the plain
| glass the right spot on the floor in front
| of the window disappears. and the entire
floors, walls and ceiling appear Of sensi-
| bly, the same brilliancy. The action of
| the ribbed glass appears to be prismatic,
the greater part of the light falling on the
ribbed glass at any point being refracted
| and spread out into n fan-shaped beam
| lying in plane nearly perpendicular to
| the plane Of the glass and to the direction
of the ribs.
! 1t has been found that the effect Of hay-
| ing the ribs horizontal is to give an i'll
crease of light at the middle hole and
| less increase at the sides. whereas the
| vertical ribs give greater increase at
! the sides and a less increase Mt the mid
die. The horizontal ribs tend to throw
| the light. which would otherwise fall
| to the floor. straight ahead far into the
| room. while the vertical ribs spread out
| the light on both sides. 1t is, however.
| useless to discuss the measurements Of
the distribution with horizontal ribs, as
| the blilliancy of the glass itself is then
so great as to be unbearable. rendering
its use in this position out of the question
for most purposes.
The diffusion of heat is much the same
as the diffusion of light. 1t was found
that there was no spot where the heat
rays from outside streamed directly in
when ribbed glass was used, and objects
near the window were cooler than when
plain glass was used by from to Is de-
grees Fahrenheit. However the ribbed
glass itself is hotter than the plain glass,
and the temperature Of the air In the
two cases was not sensihly different.
The windows Of several large factories
have thus far been fitted up with ribbed
glass and the effect in each case has
proved startling, eath room giving the
impression of almost unimpaired day
light No window shades, are required
and the results have proved wholly satis-
factory. In two instances, rooms IN fac
tories which are overshadowed by neigh
boring buildings, are now being fitted
with this glass, and it has been remark
ed that the relative increase in the ef-
fectiveness Of light is much greater
where the light is derived indirectly than
where it is derived from the sun, to
. which the windows are exposed. It has
been suggested that manufacturers might
test this matter at very small expense,
selecting one or more windows in especial
ly dark places for the purpose Of observ-
ing the effect. A very large new estab-
lishment near Boston is now being glazed
in this way. The effect is already mani
fest from partial application Of the
theory. The working men and women
in this establishment are of very high
type, hence the foreman reasoned that
objection might be taken to the complete
closing of the outlook from the factory BY
the use of this glass throughout the win
dow. The windows in this factory are
of the ordinary lifting type, therefore the
lower panes have been glazed with plain
or clear glass, while all the rest Of the
window is glazed with the ribbed glass.
The effect Of this is said to be entirely
satisfactory and pleasant ~a