The Saint Paul globe., 1899-04-23

the Hish-Frequency Electric Rip
pies to the sIow-Frequency Elec-
tric Waves-Tehe "SyntOnic" Ar
rangement of DIR. Lodges EIec-
trio Currents.
In a recent address on those delicate in
struments called "coherers" which make
one form of wireless telegraphy posi-
BILE, DR.. Lodge said that he had some
times been surprised at the wondering
interest which the general public appear
ed to feel in the sending Of telegraphtc
messages without intervening wires. Up
to certain point in this century that
was the only form of telegraphy. In the
history Of wireless telegraphs the sema-
phore and the heliograph are landmarks;
and it is no more wonderful that electric
waves should be transmitted through the
ether than the eye should catch the wink
of the heliograph on distant hill or
perceive the waving arm OF the sema-
sphore. What Is wanted for wireless tel
egraphy, as one more generally thinks
of it, Is merely an instrument which snail
receive and record electric waves, in the
same way that the eye receives and re-
cords vibrations Of light and the ear re-
ceives and records ripples of air. All are
forms of energy, says a correspondent OF
the London Post.
TWO KINDS OF VIBRATION.
Now, there are two kinds of electric
ripples or vibrations, the distinction be-
tween which may be best understood by
a reference to two kinds Of air ripples.
reed or violin string vibrating slight
ly but quickly is audible at a distance,
while a fan vibrating strongly but slow
ly is not audible at all. The analogy Is
a little dangerous. The natural impulse
of the person who observes 1t is to say:
.'Then, If you want to transmit electric
ity through space it will be more con-
venient to use the high frequency waves,
which, by the analogy Of sound waves,
have more lively penetrative power,
and can be more easily detected" That
is what many people working at wireless
telegraphy have thought during the last
few years. DR.. Hertz-who first discover
ed that these high-freQuency electric
waves could be propagated, reflected and
DETECTED just like ripples of light-set
a whole school of investigators at work.
who strove to find new means by which
the arrival of these waves at given
point could be perceived and notified. NJ.
Edouard Branly in France was the first
to hit on the delicate form of a detector
Of these ripples which Is called Co
herer." It is rather more easy to eX-
plain what this instrument Is than the
principle on which it acts, for Lord Kel-
win is perhaps the only man living who
has any idea of the import of electric
cohesion Roughly speaking, If a vacu-
um tube is filled with iron filings the
tube may be regarded as a non-conduc
tor But if a discharge of high-frequency
electric waves takes place in its neigh
borhood the filings instantly cohere and
the tube becomes a conductor. The slight
est shake or tap brings back the tube to
It's original condition. This curious cleo
trio phenomenon furnished M. Branly
and Dr. Lodge, and Profs. Righi and
Tesla, and after them several other ex-'
perimenters, with method Of signaling.
You sent a discharge of Hertzian high
frequency" waves, and the "coherer'' sig
nif1ed their arrival by becoming a con-
ductor. Among the students who have
followed along these lines has been M.
Marconi, who has made several improve
ments in the form Of the "coherer,'' as
well as in the form of the apparatus for
transmitting the waves, and who has
really been the first to adapt these sig
nails to the purposes Of systematic teleg-
raphy.
SLOW VIBRATION METHODS.
During the last twelve months, how
ever, the leaders of thought in electric
work and theory have left the considera-
ton of this brilliant and interesting meth
cd for that of the earlier ones. Elec-
trical speculation has, in effect, turned
~~xlI>~ %4,,-~ !. H. II.
pulsating fan, and rests now not with the
high-frequency electric ripples, but with
the slow-frequency electric waves. Thus
1t is at present believed that future work
in respect of wireless telegraphy will be
done along the lines of induction and
conduction, or 'earth-leakage," with
large, slow -pulsating currents. An IL
lustration, faulty In some respects, but
convenient, of what is meant by the
methods of Induction and earth conduc-
ton may be. obtained by imagining a
man to be holding hoop of copper wire
in each hand-the hoops parallel to one
another If an alternating electric cur
rent Is sent round one hoop, sympathe-
tic responsive current appears spontane-
ously in the other hoop. Mr.. W. H.
Preece, of the postoffice. might describe
this as an example Of the inductive meth
cd: and one imagines the current alterna-
ting around the first hoop, and produc-
ing field Of electric force about its
area whose lines radiate to the second
hoop, and set up a current there. Dr..
oliver Lodge, however, who, next to
Lord Kelvin, Is the most suggestive spec
ulator In the domain of electrical theory,
looks at It in different way. How
m,,ch Of this induced current he asks,
NAV not be due to leakase?-to conduc-
lion through the arms and body of the
man holding the hoops' Further, he af-
erma that without some artificial cleo
trio resemblance between the hoops. mere
induction, mere radiation Of lines OF eleG-
tzie fefoe, win never b. powsrfua enough