The evening times., 1896-02-20

their path after they leave the tubes
surface, either by magnets, prisms or any
means known at present., nor can they,
unfortunately, be converged through
lenses. The sO-caiicd Y rays are, BESIDES,
invisible to the eye, and are according to
our best authorities apparently Longitude
nal. experimentation, proving that an
object placed i'm their path cast a pecu-
liarly-sharp shadow,
HOW TO EXPERIMENT.
The experiment should be made in this
way, following very closely Prof. Roent-
gems plan. Use dark room, cover your
incandescent lamp with black paper, which
will exclude all other light rays. Place Il
sensitive plate in your holder, close the
shutter, lay some coins on the top and hold
the lamp bulb directly above, within two
or three inches from the coin; run the coil
for half an hour or so. develop the plate.
using a fresh developer free from bromide
of potassium, and after a long time the
latent image may appear. l designedly
refrain from saying it will appear, as the
process is necessarily uncertain. hnging
as 1t does upon SO many conditions.
Should the experimenter wish to go step
further he must procure Crookes tube.
which is made OF thin glass and highly ex-
hausted of air by means of vacuum pump.
Inserted through the glass and Theoretically
sealed are two electrodes or terminals OF
aluminium, spreading on the inside into two
little disks. The tubes are OF great variety,
but the one we wish to describe is four
inches long, is pear shaped. and has only
three inches between the anode aud cathode
disks, where the discharges take place.
When a static machine or powerful induc-
ton coil, capable of giving two-inch spark
or more, is attached to the Crcokes tube, it
will be noticed that a wonderfully beautiful
electric display results, covering the whole
interior of the tube. More especially is it
observable from the cathode disk.
Prof. ROentgen describes many expert
ments with opaque and semi-opaque sub
stances, experiences which are exceedingly
interesting. By placing his hand on
closed sensitive plate or film holder the X
rays passing from the CroOkes tube, held
few inches above the hand, go straight
through the flesh and paper slide of the
plate holder, casting a shadow OF the bOny
structure OF the hand, and if left suffi-
ciently long these same rays would un-
doubtedly penetrate the bones.
As the plate is protected from extraneous
light rays by the plate-holder slide it will,
Of course not be necessary to cover the
Crookes tube with black paper.
ALL BODIES PENETRABLE.
The professor found that all bodies were
more or less penetrable, paper, wood and
rubber among the rest were found to be
very transparent, metals were more
opaque, aluminium and glass of equal thick
ness were on a par, thus, by placing a
sensitive plate in a dark room, facing the
closed door. the X rays penetrated through
the woodwork, casting their shadow on
the plate. By using a fluorescent screen,
consisting OF sheet of paper covered
with a chemical known as barium platino-
cyanide, the screen becomes luminous under
the influence of the x rays when the
| Crookes tube is entirely covered with black
paper; and IL thousand-page book be
placed between this screen and the tube
| the screen will contain this stran geiy
/! luminous appearance, scarcely suggesting
| the fact that there is an opaque object en-
deavoring to Obstruct the y rays.
There are other fluorescent screens which
| have been discovered, composed OF calcium
| sulphide. uranium glass. Iceland spar and
even rock salt, and these have the same
| property of giving out this strange phos-
| phorescent glow hen within the reach or
| the X-rays. Fortunate for us is il that
Prof. Roentgen discovered that a bromide
of silver gelatinc plate becomes sensitive
| to these rays, thus enabling us to secure
these Invaluable Photographic records
] SO far, rs already stated, We arc unable