The sun., 1912-07-14

diaphragm covered with silvered foil was
upon seleninm coll placed in the focus NJ
silyered reflector. To the sclcnuim
cell were connected n pair Of telephones
and a battery. At the back Of the silvered
diaphragm was a flexible r,ibe and mouth
piece into which words were spoken
| Tho sound waves causing the diaphragm
to vibrate sent pulsations of the reflected
, light upon the selenium cell. producing
| corresponding variations in its resist ance
and reproducing audible sounds in the
telephone. Prof. Bell only used this over
very short distances.
Mr. Hammer describes other contriv-
ances based on selenium's disturbance nv
light. In 1888 Prof. II. r. Simon Of the
University of Goettingep discovered that
an arc lamp. the circuit Of which was In
proximity 10 telephone circuit. vas
caused 20 vibrate very pcrceptihly and
he devised his interesting speaking ART
by means OF which he supcrimposeds sound
waves produced by the telephone upon
the circuit in which the arc was placed
He connected the lamp circuit with the
secondary winding of an induction coil
the primary circuit being connected with
the carbon transmitter and a battery
The sounds thus produced originally were
very weak hut by employing . suitable
carbon microphone the sound was re-
produced 10 large audiences. Conversely
the are could also he used in con junction
with telephone receivers to receive sounds.
The mos; successful and extensive ex-
Periments which have been made with
the speaking arc arp those of Ernest
Ruhmer Of Berlin He has employed il
in conjunction with his selenium cells
for wireless telephony and with re-
markablc success He has succeeded in
transmitting speech over a beam Of light
a distance of over ten miles. he employs
a carbon transmi,ter and battery super
imposing waves on the arc light circuit,
and the beam of light is reflected to some
distant point where IL is received by a
paraboic reflector in the focus Of which
is placed a selenium 0ell connected with
a battery and n pair Of very sensitive
| telephone receivers.
| Inconnection with this hiRh development,
of the wireless telephone is a telegrapho-
a distance, 40 that II no one is present ia
hear the spoken word it will he duly in
scribed.
A valuable economy which is effected
! by the use Of scleni,Im ia in the gas buoys
used To mark the channels in a harbor OF
reef offshore. II used 10 he that the
only thing To do was TO ligh' the gas buoy
and let it burn day and night The buoys
required refilling about once in two
months this way. Nov a selenium eel
in the top shuts on tho gas 81 daylight
and the supply In each buoy lasts about
! five months.
Az sunset pilot light rclights the hioy
the disa ppsaYing sunlight having shut on
the current which the selenium has per.
miited all day An automatic extinguish
ing of city "A street lamps is based on the
same simple mec hanism. Selenium is alsc
used to STOP railway trains that have run
past signals. 4 cell of it in the seme
phore pole catches light from tho side
Of the LOCOMOTIVES. rings bell in the cal
and automatically puts on the brakes.
This unique and versatile metal II
found in Ves'ivian lava and in natura
sulphur in the Lispari Islands II is als'
found in Norway linked with iron. I
occurs in certain rare metals such a,
encarite (Sweden and ChileI. crooksit,
Norway. clausthalite the Hartz Noun
tainsI, Rio Tinto. Spain. Saxonv. Soutl
America and Mexico. II IL found widely
over the globe but only in small quantities
II isplacsi among he rare metals themi
oaily pure crysJ ailine seienium coats abou
81 gramme and the other ordinar,
article about 10 cents Sramms.