The sun. [volume] (New York [N.Y.]) 1833-1916, 1903-05-23
PROF. GOODSPEED EXPLAINS.
SECONDARY RADIATION INDUCED
ny X-RAYS
He Tells How He Secured fho'o-
graphs by the Light OF 'n's'p'e
Eu,snations From various Ar''
c,cs Including the Human BODY

PHILADELPHIA, May %. The first printed
statement issued over bis own signature
by Prof Arthur w. Goodspeed Of the Uni
versity OF Pennsylvania concerning sec
ondary radiation induced by N-rays since
his announcement made Last week OF i'm
portant discoveries in this direction IL here
made public. This statement was pre-
pared by Prof. Gootlspeed, at the request
OF the university authorities. for puolica-
ton in the univerAty's official organ, 1ne
Penns y'raniun, and will appear In to-mor-
rows issue Of that paper
Having occasion last winter to examine
critically some photographic records,
was surprised to find the clear outlines OF
some metallic bodies that had been behind
the plate during exposure This recalled
that had been consulted once by some
body who had found similar anomalies,
and that had been unable to throw any
light upon the subject. For obvious rea-
SONS determined now to spare no trouble
to hunt down the cause Of the effect which
| had observed, and after series OF up
ward OF one hundred progressive expert
ments was convinced that when an X-ray
tube Is in operation not only is every parti-
Gle of matter which is impinged by the
X-rays seoondarily radiant. but that also
in some cases this secondary radiation had
in all probability impaired activity OF some
sort to air particles and 10 portions OF the
wall which had not been impinged directly
by the primary rays,
THE cause, then. of the impressions on
the plate Of articles behind it was estab-
lished All Of the later experiments lead
ing up to this conclusion had been made
with the Crookes tube completely incosed
in a dark box, eliminating thereby every
trace of huorescent carnations when
one usually does not take the trouble TO
cut OF and which are always emitted by
the glass with which the bulb is made.
Next. from a portion of the space OUT
side the box, the X-rays, which. of course.
passed freely through he wood, were com
pletey cut on by heavy lead plates. properly
placed on the top Of the box, and 1t was on
these plates, screened thereby from the
X-reys, that the photographic films en-
ployed for receiving the records were
placed Above this, and to one side, freely
accessible 70 the X-rays, the various bodies
to be tested for secondary activity we're
arranged, including zinc, brass, wood,
my hand, and variety of articles too
numerous to mention. In every case un-
mistakable evidence of secondary action
appeared upon the plate.
~Presumlng, OF course, that others be-
sides myself may have been ork!ng along
similar lines, proceeded to look up care
fully the literature on the subject in order,
il possible, to determine what parts of
the investigation, If any. might claim
priority as we'll as originality. Two French
men, Perrin and Sagnac, found had dem
onstrated the property Of secondary activity
induced by the X-rays, and along some
lines Of investigation had given some in
teresting Quantitatiye values; and stu
third Frenchman, Guillox, had demon,
strnted the possibility Of using the hand
as secondary source.
None OF these three, however, seems
to have excluded the optical fuorssscenee
which always accompanies the N-rays,
unless special care is taken to cut it of I.
as already explained. lnasmueh as l
OF Townsend had demonstrated that some
differences in the numerical values given by
Perrin and by Sagnac must have been
due to difference in the primary rays
they employed, it seemed to me that putting
everything in absolute darkness. from
menting in the night, thereby cutting, on
every trace Of optical light, was. distinct
step in advance OF the work OF the men
referred to.
41n brief then, it has been shown pos
on sensitiaed film. inclosed in perfectly
dark receptacle. by means OF absolutely
invisible emanations from various articles,
including the human body which have
been excited by X-rays generated within
black DOX IN Il perfectly YOU'LL
"This apparently startling conclusion
loses much of its mystery when we con-
template that it is entirely proved at the
present time that only about per cent.
OF the radiant energy that comes to US
from the sun 10 capable OF affecting the
therefore, while bathed in portion Of the
other 90 per cent. may be capable Of diff.
fusing some Of 1t Is what any thoughtful
person will admit.
A piece OF white paper in beam OF
sunlight, or even in space diffusely IL
Illuminated, as is the room Of house, re-
ceves a small portion OF the per cent.
Of the total energy incident upon its path
and diffuses again small portion OF what
1t receives, thereby making it visible to the
eye: Why, then. might we not expect that
a piece Of zinc or copper favorably posed
to receive a portion Of the other ss per
cent j. e., Of the dark energy, should be
capable OF diffusing some part OF that IN
such way as to be effectively visible
to some appropriately devised apparatus
for observing 1t?
1T is to be noted in passing that the most
favorable location for getting. some OF the
9S per cent. without some OF the visible
per cent is in dark room. We have been
using the word dark, OF course, as applied
to the human eye. 1t is quite possible
mouse. and very likely cat. could, II it
had the proper intelligence. give us va ua-
bic assistance in rooms to us totally dark
which are doub less to them comfortably
1t Illuminated
.In connection with the work just re-
ferred to, somewhat painful personal
experience seem to me to be suggestive
as to the possible cause OF the well. known
inflammation which sometimes followa
prolonged exposure to the N-rays. A year
ago had occasion to sleep in the ~ me
room in which experiments had been con-
Quoted during the day. At the end OF that
| time I left town, but developed at once
an aggravated attack of infi mrnstion OF
| the eyes and throat, which yielded to treat.
ment after a few days. During the first
! week Of this month again found II con-
venient TO sleep in the some room where
had been conducting experiments during
the day and evening. At the end of about
the same time all the symptoms reg pPearet
with which had suffered a year ago, with
same resut-on changing sleeping roomt
the difficulty at once Disappeared
| in drawing conclusions from these ex
periences, it must he noted that no trouble
has been experienced in the meantime moi
| before, although have frequently, during
| the last six weeks, spent several hours ehcl
| day for week or two at time around the
X-ray apparatus. In the night the room hao
been nearly or quite closed, preventing tree
! air circulation, and the potent protection OF
| eyeglasses was wanting.
II am forced, under the circumst ances, &c
believe strongly that the immediate cause
| of the troublesome determinations was the
secondary emanations from the air or bot.iet
| In the room. OF the human body itself rather
! than the urinary X-r,ys This theory