Evening star., 1901-02-09
WILL WORK WONDERS
Far-Reaohing Results Of Prof, Pupin's
Great Invention.
ON TELEGRAPHY And TELEPHONY
Short Waves of Electricity of Very
High Vibration.
BROUGHT HIM A FORTUNE


ocean and substituting telegraph at the
rate of 1000 words a minute for the present
system of fifteen to twenty words minute
used in cabling across the Atlantic. His in
vention is not as revolutionary in its char
| acter was the first use of the telephone
or even as is the Introduction OF wireless
telegraph, but 1t Is important enough to
warrant general attention and valuable
enough to be acquired by the American
Telephone and Telegraph Company for half
million dollars I'D a large annuity to the
inventor. 1t is not often that a college pro-
| fessor is paid 100000 year for his labor:
Prof. Pupin is exception to the general
rule. 1t has taken him about five years to
work out the present principle. The scien-
| tific possibilities have been proved; the
| commercial side now remains to be taken
| up and applied to general use.
1t was in 1895 that Prof. Pupin began his
| series of experiments now first made known
In their successful result to the public.
Doubtless many other scientists had pom
| dered over the problems of resistance in
| wires used for long distance transmission,
| but no one saw a way of overcoming the
difficulties. With the systems now in use
only very long electric waves can be pro-
duced These waves are hundreds of miles
long and the main difficulty in finding
way OF studying their effects lies in Just
this fact-thefr great length. There were
previous TO the work of Prof. Pupin, no
laboratory experiments possible by which
to prove any ma thematical theories regard
ing them. Indeed, it was not until Helm
rlch Hertz produced electric waves short
enough to = be measured in laboratory
that the study of electric waves and their
effects received much attention. Even then
the subject was difficult of approach so far
as its application TO telephony and teleg-
raphy with wires was concerned. The laws
for the Hertzian waves do not hold for the
long waves, for the reason that the Hertz
ian waves radiated in free space and the
ordinary telephone or telegraph waves are
forced along single path or wire.
Overcoming the Difficulty.
Prof. Pupin pointed out this fact to his
fellow scientists some two years ago. and
explained then to some extent his method
for overcoming the difficulty. 1t is inter-
esting to note that the vibration of the
Hertzian wave is many millions per second
and the waves vary in length from a few
inches to few hundred feet Marconi uses
THIS form of waves for his wireless tele-
graph work. The ordinary telephone or tele-
graph wave, on the other hand, as has been
noted, Is hundreds of miles in length and Is
produced by vibrations of only a few hun
dred or few thousand per second. Now the
chief drawback to long-distance telephony
has been the blurrng of the vibrations
which act on the telephone receiver, caused
oy me ACTON OF these long waves. In teleg
raphy the main difficulty seems to have
been the loss of energy along the line. to-
gether with the great resistance of a long
line. These difficulties Prof. Pupin set about
10 overcome by an apparatus which would
produce short waves and reduce the evil
effects Of resistance.
How was he to produce shorter waves?
He brought to bear first the light of other
science on the problem. and taking the ac-
ton OF wave Of light in passing through
dlnerent mediums, thus producing various
wave lengths, he applied the principle to
electric electric waves. For example. the wave
.ength OF sodium light is shorter in glass
than In vacuum, and if one could increase
the index OF refraction of glass to anything
he wished, he could decrease the wave
length in that glass to anything he wished
As AS .ne nnedlum grows denser the energy it
stores up increases. AS Prof Pupin argued
II substance which stores up a thousand
times as much energy as vacuum be
placed IN the path of the ray of light the
waves Will be one-thousandth part as long
IN tnat substance as in the vacuum
Creating Short Waves.
Now apply the principle to electric waves.
Prof. Pupin found the necessary medium
In certain choking COLI of wire which
he inserted at intervals In his telephone
circuit. In one of his earlier experiments
he connected in a single circuit fourteen
coils of wire each of which was capable
OF storing up the same amount of energy
as ten miles Of telephone wires, that is to
say, each had the same amount of self
iCsistdHCG dllu ten
miles Of telephone Wire The coils were
placed three inches apart. making a total
length of three and a half feet He had.
then, the equivalent of 140 miles of tele-
phone wire. A wave 40 miles long would
develop it's whole wave length taking a
spiral course now, in the fourteen coils
but as 1t had gone over only three and a
half feet its rectilinear velocity and there
Tore Its rectllinear wave length was re-
duced to three and one-half feet, a reduc-
ton to less than one-two- hundred thou
sandth part of its original length. Thus
very simply, it would seem Prof. Pupin
found a way of creating short waves and
having found them, of making swift and
accurate electric communication possible
over much greater distances than before
One of the great obstacles to ocean tele-
phony was then removed 1t remained to
arrange the coils along his wire or cable
in such a manner that the right effects
would be produced, by so adjusting each
coil that the energy sent through the cir
cult would be conserved. 1t is in the ad-
justment Of the coils that the virtue of
the invention consists and the explana-
ton is too technical for general compre-
hension. 1t Is sufficient for the laymen>
to know that these Pupin coils overcome
the evil effects of electric resistance and
make possible another great step in prac-
tical progress.
Reducing the Loss.
To illustrate the invention by Prof
Pupin's present laboratory apparatus, 25O
miles OF wire are supplied with go 'chok-
ing coils one coil being inserted in every
mile Of the circuit. 1t was found that the
absorption of energy which generally takes
place along a telegraph or telephone cir
cult was greatly reduced Accordingly the
same amount of energy sent out from the
transmitter would go much farther with
his apparatus. 1t was problem of equal
ly distributing capacity, self-induction and
resistance.
In its outward appearance Prof. Pupin's
laboratory presents curious-looking ap-
paratus. Over on each of five tables stands
a box about two feet square in which is
contained fifty miles of wire, representing,
If you will, fifty miles of ocean cable. From
each box project connections for 200 wires
and these wires are attached to fifty coils,
each coil being supplied with four termi-
nails. The coils themselves look like small
earthen jars open at both ends; in reality
they are merely made up each OF two coils
Of wire of different size carefully insulated
from each other and having the effect of an
ordinary induction COIL Doubtless in the
working out the right relations between
these two sets of wires in the coil Prof.
Pupin encountered his greatest problem.
To get the effect which should give the
proper resultant on his circuit was most
Important, but once the relation was es-
tablished, the principle could be applied