The Virginia enterprise. [volume] (Virginia, St. Louis County, Minn.) 1893-19??, 1904-12-30
WOODS < III lures.
Invisible Radiations Have Detected.
That Act Upon Photo
81 graphic Plates, , .ssf

Invisible radiations that act upon.
the chemicals Of . Photographic plate.
come from other sources than urani-.
UNI, radfum, thorium and allied met
ais. They also emanate from certain
vegetable products. DR.. William ].
Russell, an Englishman, recently de-
scribed before the Royal society in
London some surprising results which
he had observed. Nearly all woods
appear to possess this strange proper;
ty, though some are more powerful
than others. An exposure from half
an hour to 10 hours is needed to pro-
cure an impression. The wood should
be in contact with the plate, or close
to it. The wood of cone-bearing trees
Is especially active. 49, =
A picture shown by DR.. Russell was
derived from cross section of a
branch of a Scotch: fir, and showed
distinctly the rings formed there by
here seems to come from that portion
which was added In the spring. and
the annual portion had apparently lit
tie or no influence. The change has
been attributed to hydrogen peroxide
emitted by the resins in the wood,
and these exist in both parts. How
ever, it is suggested that perhaps it is
confined in the autumnal half of the
ring in such a way that it cannot es-
cape.
Experiments with spruces show that
radiation occurs from all parts of the
section alike. Hence rings are not
well defined. With the larch again
there is a reversal of the behavior of
the fir. There is enough difference
between the spring and autumnal
growths to make an impression for
every year, but the latter part is the
most effective.
In addition to many woods different
resins and allied bodies can, when
used alone, be proved to be active,
some naturally much more so than
others. Ordinary resins, Burgundy
pitch, gum mastic, are active: asphalt
UNI, dragons blood much less SO, but
true gums, such as gum senegal and
gum arabic, are entirely without &C.
ton on a Photographic plate.
Several years ago DIR. Russell made
public a statement that feeble photo
graphic action had been observed in
printers ink, and that old books
would sometimes exercise it. Accurate
copies of print could thus be OBJ
tanned, although contact of several
days was sometimes necessary. At
that time it was suspected that it was
the rosins in the ink which produced
the effect.
The most novel of the revelations
made by DR.. Russell in his recent lee
ture was that wood has a property
which has hitherto been observed
only in a few minerals. If exposed to
strong light it will absorb some of the
rays and afterward give them of,
though the rays in question cannot be
SEEM. The popularity is manifested in
the following manner:
A piece of black paper or tinfoil is
laid on a bit of pine board, so as to
cover only half of the latter, and the
whole is then exposed to the light. A
Photographic plate having been after
ward applied to the wood, the portion
which was illuminated acts more pow
erfully than the rest 1t is credible,
of course, that instead of true radia-
ton being involved chemical change
is effected in the wood or some in
gredient thereof, but the phenomenon
is not the less mysterious.
DIR. Russell points out that the in
crease in activity is not uniform in
consequence of the illumination, but
that those parts that are already act
ing and which would reveal the tex
ture of the wood act more strongly.