The Providence news. (Providence [R.I.]) 1891-1906, 1896-01-31
ABOUT SCIENCE.
ExempIifed by Interesting Expert.
ments by Professor Wright.
CATHODE RAYS ARE EMPLOYED
To Photograph objects Behind
Opaque Bodies.

NEW HAVEN, Jan. 31.-Professor a. w.
Wright, who occupies the chair OF expert
mental physics at Yale university, and Is
IN charge of the Sloane physical labora-
tory, has made successful experiments in
photographing objects behind Opaque
bodies by the agency of cathode rays, In
which Professor w. @. Roentgen OF Wurz-
burg, Germany, has been reported TO
have achieved remarkable results.
Professor Wright used in his expert
ments a tube in which the exhaustion Is
carried TO so high n point that the tension
of the gas left I'm the tube is measured by
a few millionths Of ordinary atmospheric
pressure-the so-called Crookes' tube-and
connected the poles of an induction coil
in action. The discharge from tho mega
tive elcctrode Of such n tube gives the
cathode rays, which. IL must be empha-
sized, are almost non-luminous.
Professor Wright's experiments were
made with q great variety OF substances,
and it was found that strong impressions
were obtained upon a Photographic plate,
even when il was enclosed in an Opaque
wrapping OF black paper and covered with
Q pine board half an inch thick. 1t was
evident at the outset that the order OF
transparency OF different subjects for the
light rays was very different from that
which is found with the cathode rays.
Thus pieces of glass were more Opaque
to those rays than some of the metals or
than ebonite, which is perfectly Opaque to
luminous rays, but transmits the cathode
rays with great freedom Among the
metals aluminium Is especially distin-
guished, and in one of the experiments OF
Professor Wright an aluminium medal
left its impress on the plate so clearly MS
TO show both the design and lettering. In
this latter case the layer between the
medal and tho sensitive plato was abso-
lutely Opaque ebonite, which Is the sub
stance used 10y photographers to darken
completely the p~late-holder.
In other experiments which were made
by Professor Wright, with pine board In
terposed, n closed paper box, containing
aluminium grain weights, left a trace upon
the plate which appeared as though the box
was almost transparent, n the weights
themselves somewhat translucent. An
ordinary lend pencil, lying near the box
upon the interposed board, showed its
graphite core by n darker trace in the
middle of the fainter impress of the wood
OF the pencil.
n Severe Test.
Another paper box contained, imbedded
IN cotton, three small spheres, one Of plat
mum. one OF brass and one OF aluminium.
In this case. also, the box and cotton APP
peared SO nearly transparent as to leave
but a slight impression on the plate. The
brass and the platinum spheres inter-
cepted a large portion OF the cathode rays,
<ho aluyrtntu,p cnhara An ynnCh cn,allar
proportion. A number of American coins
silver, copper and nickel-produced
strong impressions, showing almost COM
plete interception of the rays; but there
were differences, the copper coins trans
hitting more than the nickel, and tho
nickel more han the silver.
In an earlier experiment a somewhat
thinner board or white wood was used.
the plate being wrapped In black paper as
before. On this board was laid n pocket
book OF dark Russian leather, with several
flaps OF leather within, and containing
seven cards, two of them thick. A num-
Der of small coins were slipped into tho
inside compartment of the book. which
was then closed and laid on the board
under the tubs. On the plate, when de-
veloped, only a faint shading was left by
the pocketbcok, but the coins left n strong
and definite fixture. showing with surpris-
Ing clearneSs their number and position
In the book.
A trace of Professor Wright's hand,
which rested upon the board during this
experiment, was also strongly depicted.
The outlines of the hand were somewhat
blurred, and In the palm faint traces of
the passage Of the rays between the bones
could be detected, but there was little OF
The effect, reported by Professor Roent-
gen, OF tho greater distinctness Of the inn
preston made by the bones.
1t may be said with regard TO the pic
lures ON the sensitive plates by these ex-
periments that they nave TO the eye an
appearance similar TO those of shadows
thrown by the object upon n surface when
the source OF light is but n short distance
away. IL the object Is bat a short distano 70
from the Illuminated surface, the image
Is somewhat enlarged, also distorted II the
rays fall %ob.iqacly, md the edges some
what blurred or diifused.
III the distance OF the tube is increased,
or the interposed Opaque layer is thinner,
so that the subject experimental upon Is
brought quite near To the sensitive plate,
then the outline OF the picture is more
sharp and clear and the proportions are
more nearly normal.
Duplicate of the Wilmington.
NEWPORT NEWS. Va. Jan. 3l-Ihe