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54
the light. This room is not quoted as shewing how a room should be lighted, on the contrary, it is an
example of bad lighting. It is bad when lighted by naked gas jets, because the light is insufficient, and
still bad when lighted by Welsbach light, because the lights are badly placed. For schoolrooms with
the usual company's gas, naked gas jets afford a poor and wasteful illuminant. In such a room as
quoted, at least four more burners would be required to obtain the minimal desk illumination. The
cost, the heat, the consumption of air, and production of fumes and soot, would all thereby be doubled.
Again the sootiness of these jets prevents the use of suitable reflectors, and a great part of the light is
wasted. Even given the minimal illumination, the light is yellow and unsteady. The colour does not
give the best contrast and the flicker is very objectionable and fatiguing.
Incandescent Gas Light.—The preceding example is enough to shew the advantage of
this means of lighting. The examination resolved itself into a determination of what form of burner,
shade, and pendant, is most useful for classrooms, and the position of the lights in the room. The
three burners examined were " C," " Kern," and " Simplex." The last is the latest pattern produced
and seems to be the best of the three as regards the light given. The light given by it, and the mantle
provided, is better than that with the others. It has the advantage of being 2½ inches shorter than the
" Kern." It has a good air regulator, which, although theoretically unnecessary, with a constant gas
pressure, is practically a most important part of the burner, and a device by which it is possible to considerably
improve the light. The burner might be improved in some details. The makers have now,
accordingly, supplied a pattern burner without the unnecessary brasswork obstructing the downward
path of the light rays, which is an improvement. With a good burner and mantle a proper shade is
the most important part of the gas fitment. For deskwork a Welsbach light without a shade is rather
worse than a naked jet, because the brasswork of the burner casts a black shadow beneath the light;
by reflection from a shade, the light can be so distributed as to be practically perfect. Such a lamp
shade for school use should in the first place be cheap and durable. It should reflect the light so that
there is no shadow beneath the burner. It should also so reflect the light that the lamp at a given distance
will efficiently cover a given area. The shade should also protect the teacher's eyes from the direct
glare of an exposed mantle. Four varieties of shades were submitted for examination— "Squat,"
" Calypso," " New No. 3," and " Reflex." Most of the shades or globes on the market are adaptations
of the old globes around naked gas jets, and variously altered or contorted to suit the fancy or aesthetic
ideals of the makers.
Diagram XVII.
The inadequacy of such a form as the "Squat" is obvious. The sides subtend an angle of 45
deg. to 50 deg. and do not reflect the light past the massive brass burner. In the "Calypso," with
something of a parabolic reflector in its shape, the opaque mass of the burner is particularly effective
in stopping the rays. " New No. 3 " differs only from the " Calypso " in the shape of the lower clear
glass portion, which is immaterial. The " Reflex " is an attempt in the right direction, but its details
have been carelessly arranged, so that in classrooms it may be very objectionable to the teachers. Effi-