The Wilmington daily Republican. (Wilmington, Del.) 1890-1902, 1896-10-08
LIGHT MINUS HEAT.
scIENcE SLOWLY SOLVING THE MYs-
Terry OF PHosPHoREScENcE.

raveled. Uncanny stories Of corpse lights
and will O. the wisps may continue to fur
nish food for the folklorist, and the tabled
lamp Of Aladdin will flourish forever in
story. Science, when she dissipates mys-
terry, always ends by leaving the heart of
the fable untouched. Nevertheless she does
explore the facts that lie at the base Of ro-
nance, and sometimes deals cruelty with
them.
OF the out Of the way corners Of science
none has been more tempting than that
which Is concerned with the strange prop
erty Of giving out light without heat. To
the alchemists are due the beginnings of
real discovery. Did not Kraft evolve from
hideous brew of organic matter the ma
terial afterward isolated as the chemical
element, phosphoruss Its slow oxidation
In moist air produces the pale CLEAN IA
miliar to every schoolboy as belonging to
lucifer matches. Did not an obscure shoe
maker Of Bologna discover that by heat
ing in furnace, mixed with little flour
meal, q certain powdered spar from Monte
Palermo, there was yielded a chalky pow
der having the property Of shining in the
dark after having been exposed 10 sun
lightP
Here was prime mystery. No combus.
ton, no waste Of substance--in short, .
mere bottling up of daylight to emit 1t
again with a feeble night long CLEAN when
all around was dark. To the famous phos-
phorus of Bologna succeeded the more
brilliant phosphorus of John Canton, con-
cocted Of oyster shells calcined with char
coal or meal In closed crucible. And the
phosphorus of Canton is in our day super
seeded by luminous paint used for clock
faces and matchbox tops, that need to be
visible In the blackness Of night. Science
tolls us that after all, these are only sui
phides Of the alkaline earths, but, be that
so, those that shine best are never pure
sulphides.
Closely akin to phosphorescence is the
property Of fluorescence, the nature OF
which, though some of the facts were
known to Goethe, to Brewster and to
Hersohel, was first explained by Sir George
Stokes A chip of horse chestnut bark,
crystal of quinine or grain of the dye
stuff eosin Is dropped into water-aoidu-
lated, 1t may DO, to hasten solution-and,
behold, the liquid exhibits on the surface
exposed to light most beautiful coloring,
green blue or orange, as the case may be.
That liquid should possess surface
color where the light first strikes it,~and
that color be quite different from the color
of the liquid itself, as seen by transmitted
light, is fact that fascinates by Its para
doxical nature. Why should the green
liquid made by macerating young green
leaves in alcohol shine with a deep red
color on its surface9 Fluorspar, the blue
John" of the miners, exhibits a similar
possession, for Its surface color Is differ
emit from the tint Of the mineral.
Stokes showed that this surface tint Is
due to the property Of the liquid in trans.
forming into visible colored light some Of
the invisible waves which are always pres
ent in daylight, and from their position in
the spectrum are called ultra violet waves,
being waves of shorter length and higher
frequency of vibration than the shortest Of
visible waves-namely, the violet. This
transmutation of visible into invisible
Stokes named fluorescence.
Then followed the discovery that these
waves, which excite huorescence, as above
described, and which are the very waves
that are most active photographically, are
also the waves that are most active in pro-
ducing phosphorescence in the luminous
paints Here was afforded o very broad
hint that both fluorescence and phosphor-
escence might BE-, like Photographic ao-
lions, chemical phenomena in their es-
Gence.
Then the patient Becquerel, using in
strumental methods for observing SUBJ
stances in the dark after they had been ex-
posed to light, and especially to ultra vio-
let waves for brief fraction Of a second,
showed that phosphorescence, SO far from
being a rare property, is possessed by in
Vulnerable kinds of stuffs Chalk, porce-
lain, glass of various sorts and rubies
shine for q twentieth of second or So
Some artificial chemical crystals, notably
the green compounds Of uranium, shine
for but one hundredth Of a second or less
Regarded from the time standpoint, the
difference between phosphorescence and
fuorescence is mere difference in degree;
the one is q persistent, the other tran
siont transformation of the waves.
On the top of these discoveries of gen.
Grafton ago came the observations, nota-
bly, those of Crookes, that fluorescence and
phosphorescence are stimulated by electric
discharges in vacuum much more brilliant
ly than by even the brightest sunlight The
phosphorescence excited by the discharge
from the cathode, or negative pole, In the
most attenuated vacuum possesses many
striking and brilliant features.
Lastly come the memorable researches
of Lenard and Of Roentgen, who have
found in the carnations that proceed
from properly exhausted vacuum tubes,
when electrically stimulated, rays that
will penetrate paper, wood, flesh and even
opaque sheets of aluminium and will new
crtheless make their presence known by
causing flporescence and by their photo
graphic action.
Roentgen's worldwide discovery seems
almost like an inverse species of fiuores-
cence-a trapsmutation from the lower to
the higher order of waves. And, indeed,
H. Besquerel has shown that the highly
1uorescent compounds Of uranium will,
after exposure to light, give off for many
hours visible waves which closely resemble
Roentgen's rays in their power of penetra-
ton through aluminium and other Opaque
materials and In their Photographic action.
So to the phenomena Of phosphorescence
and fluoresccnce we have now hyperphos-
phorescence to record And II Wiedemann
and his collaborators have half solved tho
mystery Of phosphorescence by showing
that it Is due to sort of limited chemical