The daily morning journal and courier. [volume] (New Haven, Conn.) 1894-1907, 1904-10-29
STRANGE PHOTOGRAPHY.
Sensitive Plates Affected by Resin
Gus Woods.

Sensitive Plates Affected by Resin
GUS Woods.
Invisible radiations that act upon
the chemicals OF a Photographic plate
come from other sources than uranium,
thorium and allied metals. They also
emanate from certain vegetable pro
ducts. DR.. william ]. Russell, an Eng
Iishman, recently described before the
Royal Society in London some sur
prising results which he had observed.
Nearly all woods appear to possess this
strange property though some are more
powerful than others. An exposure of
from half an hour to eighteen hours is
needed to produce an impression. The
wood should be in contact with the
plate, or close to it. The wood Of cone
bearing trees is especially active.
A picture shown by DIR. Russell was
derived from a cross section of a
branch of a Scotch fir, and showed dis
tinctly the rings formed there by the
annual growth. The radiation here
seems to come from that portion which
was added in the spring, and the au-
tumnal portion had apparently little or
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tributed to hydrogen peroxide emitted
by the rosins in the wood, and these
exist in both parts. However, it is
confined in the autumnal half of the
ring in such way that it cannot es-
cape. Experiments with spruees show
that radiation occurs from all parts of
the section alike. Hence rings are not
well defined. With the larcf. again,
there is a reversal of the behavior of
the fir. There is enough difference be-
tween the spring and autumnal
growths to make an impression for
every year, but the latter part is the
most effective.
| In addition to woods many different
resins and allied bodies can, when used
alone, be proved to be very active,
some naturally much more SO than
Others. Ordinary rosins, Burgundy
i pitch, gum mastic, are very active
! asphaltum, dragons blood much less
so, but true gums, such as gum senega
and gum arababic are entirely without
action on a Photographic plate.
/ Several years ago DR.. 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 obtained, al
though a contact of several days was
/ sometimes necessary. At that time IL
was suspected that it was the resins in
the ink which produced the effect.
The most novel of the revelation
made by DR.. Russell in his recent
lecture was that wood has a property
which has hitherto been observed only
lin 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
seen. The peculiarly is manifested in
the following manner: Al piece Of
black paper or 'tinfoil is laid on a BIZ
Of pine board, so as to cover only halt
OF the latter, and the whole is then ex.
posed to the light A Photographic
plate having been afterward applied to
the wood, the portion which illuminated
acts more powerfully than the rest. II
is credible, of course, that instead of a
true radiation being involved, a chenai.
cal change is effected in the wood OF
some ingredient thereof, but the phe.
nomenon is not the less mysterious
DR.. Russell points out that the increase
in activity is not UNIFORM in consequence
Of the illumination, but that those
paris which are already active, and
which would reveal the texture of the
wood, act more strongly. Bodies like
sugar, starch and flour. which contain
neither rosin nor allied substances, dt
not behave in this manner.