Evening star., 1902-01-25

and from less than three inches in length,
up TO over ten feet. giving from less than
ten-candle power up to fully 5000 Lamps
or innumerable shapes and dimensions have
oeen constructed and great variation OF
candle power for various diamsters OBJ (
why lamps may not be made of any size
and Of any desired candle power ...e only
limitation being that OF soften.ng the glass
produced.
In the incsndesceut lamp the carbon III
ament Is highiy resistant to the electric
heats the filament so that light Is Generate
ed In the new lamp the mercury vapor
takes the place OF the ilameHt- Its resist
ance. however Is very much greater than
the resistance OF the carbon and when suf-
hcient current Is passed a much more bril-
liant light Is produced. 1t was thought to
be impossible to use the constant current
because the very resistance Of the vapoE
Kept this current from passing through
discovered a peculiar fact, however.
and working therefrom solved the problem
found that the resistance Of the mercury
xapor was only. as II were, monentary.
That is, the moment any current at all was
passed through the tube the current Itself
seemed gradually to break down the re-
slstance until at last the resistance became
SO small that even a constant or incandes-
cent current would light the tube. At pres
ent / use small spark or induction coil
TO open the path Immediately for. the cur
the tube ordinarily will not light until
spark from the coil is first driven through
to break down the resistance, TO blaze a
way so to speak for the current. OF course,
the wnode operation is instantaneous"
Intensely White.
One OF the spark coils was attached 90
the lamp on the wall and when Mr. Hew-
lit turned on the switch 70 light the lamp
the swapping of the sparks could be heard.
The intense whiteness Of the light became
the subject OF comment. 1t has always
been said that tube lighting would be un-
desirable because of the absence of red
rays. Mr.. Hewitt was asked about this.
He replied:
THE light produced by pure mercury gas
comprises orange-yellow, lemon-yeliow,
green, blue, blue-violet and violet: and AL
though ali shades of these colors may not
be present, their absence would not be SO
seriously felt were IL not for the absence
OF the red. For some purposes the lack
OF red In the spectrum is objectionable but
LOT many uses 1t is positive advantage.
FOR shopwork, draughting. reading and
other work where the eye is called on for
continued strain the absence of red is an
advantage, for l have found light without
the red much less tiring to the eve than
with Ii. 1t is possible to transform some
waves of this light, especially the yellow
hgnt- into red light, and thus in a measure
70 overcome this defect where required for
general indoor illumination. A moderate
amount OF ordinary incandescent light in
terspersed with the mercury yanoT alac-
trfcally serves to supply the deficiency. ana
tory.
For street lighting purposes the mer-
curry light Is available even witho,ft the
red, and it should be noticed that this
Hght mas very great penetrating power and
seems to be effective through greater dis
tances that an equivalent amount of meas
ured candle power from the ordinary in
candescent lamp. This may be due to the
NJ Of h..
less penetrating than those waves which
are present in the mercury light and henca
the least valuable portion of the spectrum.
having such Illuminating effects is ornftted
ana the energy is practically expended I'm
the more useful portions of the spectrurs
nave made lamps in which this color OBJ
lection has been overcome, sacrificing on
some occasions the extremely high light ef-
flciency obtained in this particular lamp.
Without doubt lamps of this type WIFI be,
produced whose light will be even more,
beautiful than This light is objectionable.
The fact that different gases or vapors
produce different colors opens the way for.
experimentation in this line / have pro-
duced lamps of various eolors. Hydrogen
gas gives large amount OF red rays; so
does nitrogen. / have made blue lamps
and yellow. This feature of the color rays
will be improved with time. There is a
precedent in the Welsbach lamp which was
very blue when II was first used and i'm
the Nernst lamp. which has also been i'm
proved Even the Edison incandescenr
lamp was defective in its color quality when
first invented"
Running Cost Less
In the opinions of many scientific men.
the invention Of the Hewitt lamp is the
greatest electric-ligkting achievement since
the Edison lamp was given TO the world.
The cost of running the new light is now
but one-eighth of that of the Edison lamp.
power for power 1t must therefore be
more economical than gas: even as cheap
as kerosene. The darkest parts of cities
could be lighted as well and even more
economically than their main streets Light
houses Will be able to shed their rays
many more miles out to sea than they do
at present. The danger of collision be-
tween steamships will be minimized. In
short, there Is almost no department of
public or private life that would not be
benehted by such an illuminant