New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1903-05-20
BARKER on G0ODsPEED.
The Key to Recent Experiments with Roent-
gen Rays.
10y TELEGRAPH TO THE TEIBUSE-I


philadelphia. May 19-Professor Barker. the
head Of the department Of physics at the UNI
versitv of Pennsylvania is reticent in expressing
himself upon the experiments in radio activity
made by his associate. DR.. GOodspeed- he says;
1T is not fair 10 talk about the work until Or.
Goodspeed has written his hnal report 70 be
embodied in the proceedings Of the American
Philosophical Society. All scientific experiments.
as to their scope and novelty. are likely to be
somewhat exaggerated in the public mind. and
it may be that this has suffered somewhat from
publicity.
In the interesting paper read by DR.. Good
speed before the American Philosophical Society
on Friday night. he described some interesting
results which he has obtained going to show
certain peculiar exhibitions in the neighborhood
of the Crookes tube when in action. due to TIRE
ravs which are emitted by the said tube.
Or Coodspeed has been a very diligent stu
dent OF the subject OF radiation for many years.
and has produced some OF the finest radio
graphs by means Of it which have ever been
obtained. He Is at present the president OF the
American R0ntgen Society
ut has been known for some years that these
R0ntgen rays are capable Of rendering all SUI
rounding objects radioactive; this radio-activ-
ity being only transient. and ceasing as soon
as the current ceases in the tube. Thus. for in
per or iron. be placed so as to receive the X
ravs. IL becomes radioactive and emits rays OF
lis own which are known IS secondary rays
They differ from the original y rays principally
in the fact that they have less penetrating pow
er. and they do not pass as thick layer OF in
terposed matter although they do pass through
metals and other Opaque bodies
IF. now. a huorescent screen-that Is to say,
a screen capable OF converting these rays, or
dinarily invisible, into light rays-be placed in
their path this screen shines brightly The lu-
minosity is due to the secondary rays emitted
from the metal plate. 1t will be understood
that the screen is protected from the direct ac-
ton Of the Y rays themselves by a plate OF lead,
which is impervious TO them
DIR. Goodspeed's experiments and the slides
which he has taken by their means show very
distinctly the action Of the secondary or induced
rays. All the objects in the vicinity OF the X
ray tube seem 20 become active under the IN
huence Of and radiate these secondary rays upon
the protected Photographic plate, even in unex-
pected directions. He showed. for example, that
even his hand could be made radioactive, and
he was able to nave a radiograph Of several OBJ
jects by means Of the secondary rays emitted
from them.
THE whole subject Of excited or secondary
radiation has acquired great interest recently.
il connection with the subject OF spontaneous
the Curies J. J. Thompson. Schmidt, Rutherford
and others Nine. Curie has pointed out. for ex-
ample, that the presence OF an active salt OF
radium In her laboratory was sufficient to affect
all the material Of the laboratory. metal pipes.
glass, fittings, clothes and even the persons OF
occupants Of the room So strong was the
radio-activity excited upon them by the rays
emitted by the radium that ii was quite impOs-
sible to approach the electrOmeters for the pUT-
pose OF measurements.
THE difference between the secondary rays
and those which are excited by the radiation
from radium the Becqueral rays. as they are
called, is that the former continue only as long
a
excited by radioactive substances may con-
tinue for long time"