Alexandria gazette. [volume] (Alexandria, D.C.) 1834-1974, 1910-06-29
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Mr.. Belts answer such questions as
are asked him.
Mr.. Harlow: Will you explain
briefly the meaning of light and il
Illumination growing into the question
of candle power and how did it first
come to be used, and whether it is
used now. Just state what it means.
Mr. Belts: The matter that MIR.
Harlow asks about is difference
between intrinsic brilliancy and can
die power. When these new arc
lamps were first installed most of
the members of the committee said
that they did not appear to be as
bright as the old lamps. Generally
speaking it was said by great many
people | could not look at the old
lamps without shielding my eyes, but
these don't affect my eyes, apparent
". / want to explain what that is
due to: That is fact just as they
stated and the reason for it is that
the eye does not measure candle
power. It measures what is called
intrinsic brilliancy The candle
power is the total candle power given
by the lamp in any given direction.
The intrinsic brilliancy is the candle
power per square inch of the sur
face. Take a piece Of steel and heat
it to a white heat, the total candle
power might be ten Of fifteen candle
power, and the intrinsic brilliancy
might be hundreds of thousands of
candle power. The ordinary gas
flame has an area of two or three
squart inches, say it given 16 candle
No f,at &c in nfrin 10
The actual candle power only amounts
actually to five or six. You can look
at any light whose intrinsic brilliancy
is not more than seven or eight with
out the slightest inconvenience. The
customary 16 candle power lamp is
given off of such small area that
the actual candle power per square
inch is somewhat between two and
three hundred. Take the ordinary
lamp. If it gives anywherer near a
thousand candle power you could not
look at it at all. The intrinsic bril-
liancy of the sun is somewhere be-
tween five and six hundred thousand
candle power. The eye measures the
brilliancy of the source Of light per
square inch and the pupil of the eye
contracts, more or less, depending
on the intrinsic brilliancy. Every
brilliant light makes the candle power
small-with the old open arc lamp
in use is this city before the new
system was installed when you look
ed at the lamp you got the effect OF
the intrinsic brilliancy while in the
enclosed arc lamp, it is much lower,
it appears not nearly so bright. The
only way in which you can determine
as TO the merit of the two lights is
by standing off at some distance and
looking at something on which the
e ldistahfcSa% U uig Sacn a. L Lsl
on the distances between the ramps:
The form Of contract recommended
by the National Association would
make the amount of illumination
delivered at certain dstance-say one
hundred and fifty or two hunder
feet-the measure of the amount of
service. 1t is very different to meas
ure the actual candle power of an
arc lamp. 1t is very much less than
people think it is, due TO the intrinsic
brilliancy. There has always been
the opinion by those VINO looked at
the LAMPS that an arc lamp had a
Candle power WI lIlhIIi Ii.S4Si NAsNH
it would actually measure.
Mr.. Harlow: In your oponlon does
the enclosed alienation Grc lamp SER
les Of is ampere give greater or
less amount OF light than the 9.I6
open arc Schuyler light?
Mr.. Belts: At one hundred and
fifty feet the illumination delivered
les about twice as great as the old
lamp. AT the point Immediately un-
der the lamp is it not as great, but
at a point one hundred and fifty feet
away the Z amphere light gives
about twice as much light.
Question: For effectiveness in
street lighting is the lamp which we
have at present in the lily better or
not as good as the old style lamp. !
mean the one that they had here be-
fore.
Answer: That was &C ampere
lamp, that was called a 1000 candle
power lamp. This system of course
would be an improvement on the old
system.
Questions by Mr.. Fisher:
Question: On January so, in your
letter you made recommendations
that coiled pig tail holder be put III,
that the trimming Of the lamp be
changed, and that new dash pots be
put in the lamps. You state that the
coiled pig tail holders were put in?
Answer: Yes, sir.
Question: They were put in, were
they?
Answer: Yes, sir.
Question: To your knowledge?
Answer: Yes, sir. The method
of trimming was not changed TO my
knowledge, but the dash pots were
put in.
Question: How about the gas
caps?
Answer: AS far as they were
burned up in the lamps they were
put in. There was considerable trou-
BILE in the burning of gas caps, and
if the trimmings had been changed,
as directed a great deal of that trou-
BILE would have been eliminated, but
the burning continued to a great ex-
tent. Sluggishness of the lamps was
materially improved at that time, but
it was entirely eliminated.
Question: Why not?
Answer: Due to some sluggish
ness in the regulators at the ~
Question: Was any effort made
to change the regulators?
Answer: A man who was here
from the Fort Wayne factory said
they they were operating as well as
he was able to make them operate.
Question: They were never adjust
ed, were they, after this change IN
the system?
Answer: There was nothing to adj
Just. | suppose the trouble was in
the design.
Question: Were they ever made
satisfactory?