Free press., 1901-11-16
CHEAPEST LIGHT
The illumination EmiTted by tD'
Common FirefIy


ee1laneous Collections as the result Of
recent experiments, most interesting
and valuable memoir on the light emit
| ted by the FREELY, which in its conclu-
sions is, Of course, equally applicable to
all that class of phenomena, organic and
inorganic, usually referred to as being
cue to phOsphorescence.
In introduction the authors state that
the object Of this paper is to show by
the study Of the radiation of the frefy
that it is possible 10 produce light with
out heat other than that in the light it
self; that this is actually effected now
by natures processes, and that these
are cheaper in economy of energy and
consequently Of cost than our industrial
ones in degree h2hertoo unrealized.
They then go on to explain how the
waste in Illuminating power in present
methods of lighting is very excessive.
exceeding in some cases SO parts in the
100, SO that for the energy expended at
least one hundred times more light
should in theory be obtainable titan we
methods of illumination.
at is now universally admitted" thu
paper proceeds, ''tha5 wherever there is
light there has been expenditure Of heat
in the production of radiation existing
in and as the luminosity itself, since
both are but forms of the same energy:
but this visible radiant heat which is
Inevitably necessary is not to be con-
sldered as waste. THE waste comes from
the present necessity of expending o
great deal of heat IN invisible forms be-
fore reaching even the slightest visible
result, while each increase Of light
represents not only the small amount %
hea. directly conc erned in the making
o. the light itself, bit a new indirect ex7
penditure in the production Of iavisibla
calorifc rays" 3" Certain pfenon'
ena, long investi gated, yet little tnder-
stood, and grouped under the general
name of ''phosphOrescent," form an ap7
parent exception to this rule, especially
where mature emplys them in the lfv'
ing organ4sm for il seems very difjcall
to believe that the light Of a FREELY, foE
instance. Is accompanied by a teInpeE2' :
lure of 1900 degrees Fahrenheit, whitI
is what we should have to produce a
gain it by our usual processes.
The authors then give IN brief thl
history of previous Investigations re;
garding this insect light and take u1
their own experiments, which they CON-
slider under two heads, ''PEDt0me5ric'
and Thermal. using for their purpose
the Cuban FREELY, PTEoyhorus -coctiIEcus
which has a length Of about an inch AMI
a half, with a width CT half an incl,
and is provided with three light rese T:
yoirs-two. in the thoraE and one in rhs
abdomen.
Upon st viewing ne light Of the in,
sect in the speetroscope. the invests al:
ors noticed that the spectrum CONSISTED
essentially of a broad band IN the green
and yellow, which extended into anI
beyond the blue and orange. but net
greatly farther. 1Tlis Indicated the ab
sence of the heat waves Of the red anil
enfra red end Of the. spectrum. But thi
question arose as to Wnether the hglI
would not extend faTffAar we're it brig1l II
enough to be seen, and called attention
to the fact that for comparison vi, II
other spectra equal :briiliarcy had 10 Jal
obtairsed AS it is impossible % incraaEii
this quality by any optical device, thGTl
had recourse to the novel exERdient %
decreasing the brightness OF other IiSI =
to that of the insects. This Wa3 d0E.I
by placing a screen with a circular 'dia.
phram covered with ground glass in I
path OF the other sources OF light, a.
by a suitable arrangement of lens es, tbs
equality Of the lights obtained being de.
termined by photometric comparison |
This necessary condition having been
secured, the spectra of the t-3o lights !
were next brought into the field, wiz |
the result of showing, in the ease Of tn;
solar spectrum, that when its light il |
intrinsically Of the same brightness 2I
that of the insect it extends somewhat
farther toward the red and distinctly
farther toward violet, while that Qf thai
insect is more intense than the sun fol
equal lights in the green, thoWsh it eng
more abruptly on the violet side.
The professors made comparis1n,
with other lights, with tie same geues a
results, and conclude this part of thea
memoir as follows: The imr.ortan
fact, however. seems to be brou ght ou
almost beyond question that whe7
spectra are formed from two equa
lights, one from the sun, the other from
the insect, the Fatter's spectrum tern1n
ates both at the upper and lower lint
at which the solar light is stFn con
spiouous. The conclusion ToIlq.ws tina
the insect spectrum is lacking; in thr
rays Of red luminosity and resumabl,
IN the mira red rays, usua Ily of rela
lively great heat, or that it seems prob
able that We have here liz int withou
heat other than that heai which tn
luminosity itself comprise ;. and whic.
is but another name ror the sam
energy.
"Anv o+bor e.x,,~ ,,--A-s