New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1894-01-21

but Mr.. Johnson describes possible application OF
the latter one He has not yet tried the experiment
and puts the idea forward with modesty yet very
understandingly.
To begin with. he would project his picture with
a strong light through lens upon small ground
glass screen in front Of the transmltter The most
important element In the construction OF the latter
would be a selenium cell. Selenum is n substance
whose electrical conductivity is affected by varia-
lions in light falling IT, II piece OF selenum
be placed in an electric circuit therefore. the IN
tensitv Of the current will vary with that OF any
luminous rays falling upon It. And II each minute
portion Of a transparent picture. lighted from De-
hind he exposed separately through an aperture TO
a selenium cell the grndations In electrical in
tensty will correspond TO the lights and shades OF
the illustration In making such exposures. by
the way It would be desirable to have each one al
ternate with a complete shutting Off or all light
from the selenum. 50 that the current would be
broken I'D into n series Of pulsaions. varying. OF
course In strength very delicatcly. Now. Mr. john
sons idea is that such cell might be suitably
mounted In a cylinder whose sides were perforated
somewhat as I'm our diagram. but more extensively
There should be casing Just outside OF the cyl
inder with horizontal slit extending the width
OF the picture the ground glass. Owing to their
diagonal arrangement. only one OF the holes would
he opposlte the slit at a time but only small part
OF n single revolution would be required TO present
10 the slit all those In one row. IL the frame mold
ING this cylinder had a slow and properly regulated
downward motion the first row OF holes could De
made to record in straight horizontal line the In
tensities OF light and shade across the top OF the
picture: and the next row OF holes would register
another series OF points along straight line a
little lower down: and on. to the bottom OF the
picture.
At the receiving end Of the line there should be
n cylinder similarly perforated and rotated at pre-
ciselv the same rate Of speed. 1t should contain
n light that would CLEAN through the holes on 10
the receiving screen but only one hole AT time
would let light through. and that hole would cor
respond In position exactly the one In the trans
mitter which 1T that identical instant was open 10
the picture. Finally. within the receiving cyIhdrr
there. should be some means OF varying the brilI-
fancy Of the illumination according 10 the intensity
OF the electric pulsaion The relative brightness OF
each point in the original would then be faithiulV
reproduced In the copy Every child knows mat
the glowing end Of a stick which has been thrust
in the fire may be whirled rapidly enough 70 fnake
n ring of HIGHT. Impressions from dlHefeht points
in the orbit come the eye In such ciose
that they cannot be separated by our perc.p'.,,H'
johnson voud have his dots of light projected upon
the screen with such rapiGity 10 secure Slnli-
larlv simultaneous effect. While this ErIt'rlh'i
frankly says that there are some hliHVu,.nS ~
to b. overcome. his suggestions are "o' '''' '''
cstng but valuable III. o, ,t~aror,
clenium is unequally affected by light OF dinereht
cOors II would b" necessary. h.t III .'s
such apparatus to mOnochromd.ic HEht anu -
such lantern slides as Mr. Gray used IN me syS,"m
OF color photography recently des.Ilpeu ~ n
Tribune could be reproduced by MI Johnson
method and then united In c0hposlp' ~, ~
Assistance OF color screens. and thus pictures III
colors could be telegraphed TO any distance prooa
biz by cable.