Evening star., 1896-11-03
ELECTRICAL SCIENCE.
The Mystery of PhosphOrescence fs
Gradually Getting Cleared Up.
From the Philadelphia Evening Telegraph

Tne MysterY OF PhOsphOrescence In
Gradually Getting Cleared Up.
From the Philadelphia Evening Telegraph.
Bit by bit the old mystery which sur
rounds the subject of the emission of light
by phosphorescent substances is being un-
raveled. Uncanny stories of corpse lights
and ill-o'-the-wisps may continue to fur
rish food for the folklorst, 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 romance, and sometimes deals cruelty
with them OF the out-of-the-way corners
OF science none has been more tempting
than thai which Is concerned with the
strange property of giving ut light with
out heat. To the alchemists are due the be-
ginnings of real discovery. Did not Kraft
evolve from hideous brew of organic mat
ter the material afterward isolated as the
Chemical element, phosphorus? Its slow
oxidation In most air produces the pale
CLEAN familiar 10 every schoolboy as be-
longing to luclfer matches.
Did not an obscure shoemaker of Bologna
discover that by heating in a furnace mix
ed with a little flour meal, a certain pow
derei spar from Monte Paterno. there was
yielded chalky powder having the prop
e1ty of shining in the dark after having
been exposed to sunlight? Here was
prime mystery. No combustion. no waste
VI snort, n mere bOttling up
OF daylight to emit it again with feeble.
nl2ht-iong CLEAN when all around was
dark. To the famous phosphorus of Bolog-
ma succeeded the more brilliant phosphorus
OF John canton, concocted of oyster she lis
calclned with charcoal or meal in a close
Crucible. And the phosphorus of Canton Is
IN our day superseded by luminous paint
used for clock faces and matchbox TONS
that need to be visible in the blackest of
night. Science tells us that after all these
are only sulphides of the alkaline earths:
but, be that SO. those that shine best
never pure sulDhideS.
Closely akin TO phosphorescence is the
property Of 1uorescence, the nature of
which. though some of the facts were
known to Goethe. to Brewster and 10 Her
schei. vas first explained by Sir George
Stokes. chip of horse chestnut bark a
crystal of quinne. or grain of the dye
stun eosin, is dropped into water-acidu-
lated. may be. to hasten solution-and
hehold the liquid exhibits on the surface
exposed 10 light a most beautiful coloring
green, blue or orange. The case may be
That a liquid should possess a surface COL
or where the light first strikes it. and that
color be quite different from the color of
the liquid itself. seen by transmitted
light. is fact that fascinates by its para
doXical nature. Why Should the green IT,
quld Nude by macerating young green
leaves in alcohol shine with a deep red col
or on its surface? Fluorspar-the "blue-
john of the miners-exhibits a similar pos
session: for its surface color is different
from the tint of the mineral Stokes sbov-
ed that this surface tint is due to the prop
'rty Of the liquid in transforming into ,-isi-
hie colored hight some Of the invisible waves
which are always present in daylight and
from their position in the spectrum are
called ultraviolet waves; being waves of
shorter length and higher frequency of vi
bration than the shortest of visible waves
an'ely the violet. This transmuta tion of
visible into invisible Stokes named fiuores-
cence.
Then followed the discovery that these
waves which excite fiuorescerce as above
described. and which the very waves
that are most active photographically ar.
also the waves that are most active in
producing phesphorescence in the luminous
paints Here was afforded a very broad
hint that both fuorescenca and ahcsphor-
escenc" might be, like photographs ac-
tons, chemical phenomena I'm their essence
Then the patient Becquerel. using instru-
mental methods for observing substances
IN the dark after they had been cXposed TO
llSht, and especially 10 ultra yiolet waves
'or brlef fraction of a second, showed
mat phosphorescence, so far from being n
rare property, Is possessed by innumeraDle
Kinds Of stuffS. Chalk, porcelain glass of
various sorts, and lubies. shine for a twen-
teth OF q second or Som. artificial
chemical crystals. notably the green com
pounds CT uranium. shine for but / 1uoth
of a second or less. Regarded from the
time standpoint, the difference between
pnosphorescence and fiuorescence is a mere
CliIerence IN degree. the one is persist
cnt, The other "A transient. transformation
OF the waves. On the top Of these discoy-
eIies Oh generation ago came the obaerva-
items. notably those of Crookes that fluor-
escence and phosphorescence are stimulat ted
by electric discharges IN vacuo much mere
brilliantly than by even the brightest sun
lsht. The phosphorescence ex cited by the
discharge from the cathode or Negative
pole IN he most attenuatai yacuo NOS
sesses many striking and brilliant features.
Lastly come the memorable reSearch of
Lenard and CT Roentgen. who have found
IN the emanationS that proceed from prom
cry exhausted vacuum tubes, when cleo
trically stimulated, rays that will penetrate
paper wood. flesh. and even opaaue sheets
OF aluminium. and will, nevertheless make
tfeir presence known by causing fiuores-
Gence ana by their Photographic action.
fioentGens worldwide discovery of the
present year seems almost like an inverse
species of fuoresoence-a transmutation
from the lower to the higher order of
waves And. indeed, H. Bec1uerel has
SHOWN that the highly f,uorescent com
pounds VIII, after exposure to light give off
Tor many hours visible waves which closely
resemble Roentgeu's rays in their bower of
penetration through aluminium and other
opaque materials and in ;hcir photographic
action SO to the phenomena of Dhosphor-
escence and nuoreScence We have now a
nyper-pnoSphoreScence TO record. And If
Wiedemann and his collaborators have half
solved the mystery of phosphorescence by
showing that it is due TO a sort of limited
chemical decomposition of molecules under
the influence of electric or luminous sirnli-
l&tion. the mystery is certainly no less be-
wilterinS than before: the explanation is
Itself no less mystery. needing in turn
to be explained