New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1896-03-21

will emit ravs upon the Photographic plate. but may
Thl is proved by number OF experiments. OF which
the following is one; The tube Of shape roughly ~
ihr zone Of G but thin at b When this tube Is
exhausted and excited. the thin psTt a. wn,sh
graphic power Is active; while the glass becomes O'
the glass at may become melted BY the d neat pIt
It's effect on phoiographic pat' Is Wa1Is
one-eighth Of an inch thick became unmanageaoie
bv excessive heating and rapid melting ,,, =. -
hsusiion he photographic power Of the tube e.
the swiftness with which is produced developaoie
mag is roughly proportional 10 the square OF tne
auorescent cande-power or total visible huorescent
light given out by the tube 49,, ,o,,, ,, ,o
as follows With The mos, sensitive psss IN ah sn
uvht-ticht cover of about one-thirty-second or an
inch In thickness the time necessary Tor obtaining
u good Photograph Of metal grating or grd Is less
than one second. when the tube Is within one
quarter OF an inch OF the grating and about three
cighths OF Inch from the sensitive plate a, two
graph is approximately 10 seconds and at three iee
$50 seconds For rough ,ms Oh he
| square OF the distance.
| ) or the Photographic plates as ordinarily EN-,
Moved for photographic purposes. the medium rapid
plates appear to be the most suitable for Rontgen
plates to and f2 sow pas equally
unfavorabe In regard TO constituencies f1r Rontsen
s"S COMPOSITE sensitive plate was made from five
strips cut from plates Of different Photographic sem
sitiveness and Photograph OF series OF metal bars
| was taken with the bars at right angles TO the
| strips OF the composite plate. For the same expo
sure and same development. the definition Of the
Photograph produced did bear apparent rela-
ton to the Photographic sensibiies OF the strips
| according to their senstometer numbers The me
| dunn rapid plate gave. however much the densest
| Image in every such experiment
The power Of a tube having given degree a ex-
haus,ion and disposition OF electrodes increases with
the surface area OF it's huorescent walls: thus a
large vacuum tube exposing large total huorescent
| surface has rapid action on the sensitive
plate t. e. requires less exposure but Will require
| more voltage and more electric power to excite On
tho other hand for given distance of the tube from
the plate the image is sharper and less distorted as
! the tube diminishes in size Consequently, Tor a
| given tube used without diaphragm. long distance
and long exposure produce the sharpest radiograph
| small tube will produce sharp mae AT lesser s
| distance and for rapid exposures very small tube
at a very short distance is the best The smallest
| tubes experimental with have been about one men
| in diameter with about two inches between cleo
trodes and with thin glass walls small tune re-
| TO suit almost any induction coil. -
= For a given thickness of glass wall German
glass aDpears to give better results than lead glass
| The German glass employed gives yellowish fuor-
essence while lead glass gives greeni is nuores.
cence These glasses phosphoresce vsibiy Tor at
| least minutes after the cessation or the ms
charge through the tube The residual phosphors;;
cence has not yet been found to produce a visible
| Photographic Image.
The form OF the tube arrived at by gradual
| process of selection Is shown in Figure Inc
| length is about three times the diameter This tube
is made In various sizes. When the glass walls are
thin for producing the best radiographlc effect.
| spark is apt pierce the wall and destroy the
vacuum. Partly on THIS account tinfon caps are
foil caps are in connection with the electrodes. and
| cemented to the external surface OF the tune
| by shellac.
| . II was found in numerous trials with many
| tubes that the nuorescent and photographic power
OF all the tubes without caps was greatly Increased
(roughy doubled. In facD by bringing two metallic
disks connected with the respective electrodes. to
| the opposite points, represented in Figure g. The
| suppostion is that the tube thus becomes at once
| an ordinary and eectrodeless tube combined. The
| metal caps above mentioned were the outcome OF
| these experiments and not only have all these
| capped tubes remained unperforated but their
| hrorescent and photographic powers have been
enhanced by the caps -
| 10 The exciting apparatus consists OF a large
Ruhmkorr coil capable Of giving twelve-nch
| spark although such length OF spark Is rarely
! required The coil Is excited either from storage
battery through an interrupter. or preferably from
a l2O-vot contnuous-current circuit. through q
! bank OF from eight to twenty sixteen-candle-
power incandescent lamps arranged In paral-
/ lei. with IA rapidly rotating wheel ntcrrupter
driven by small motor ABOUT f9 IN
terruptons made per second. and the
duration OF closure In the circuit is twice that
of opening An air blast Is directed upon the spark
over the periphery of the interrupting wheel
| through fine nozzle. This tends to produce sud
den breaking Of the circuit II has been found that
greatly Improved results have followed the removal
OF the usual condenser and the substitution of the
air blast.