The morning news. [volume] (Savannah, Ga.) 1887-1900, 1900-05-27
PROF. PUPIN's DISCOVERY.


Puzzled Science Is Believed To BE
Solved in Part, at Least.
From the New York Sun.
For a number of years Prof, NJ l. Pu-
| pin of the Department of Mechanics of
| Columbia University has carried on a Sc
ries of experiments dealing with electrical
waves of considerable length, and has as
certained from these studies that by means
| of cables and long distance air lines con-
structed in a peculiar manner it is posi-
| BILE to increase to a marked degree the lin
its over which telephony can be conduct
| ed, besides adding greatly to the useful
ness of submarine cables by making them
available for many more messages. The
final results of Prof Pupin's investigations
were announced last Friday at the an
| nual meeting of the American Institute
of Electrical Engineers IN Philadelphia
AT meeting last year Of the same body
| Prof. Pupin read a paper on The Propa-
| cation of Long Electrical Waves" and at
the recent annual meeting of the American
! Mathematical Society, he described the
purely mathematical questions involved in
his investigations,
| In addition to the mathematical and ex-
perimental solution of certain questions
| that have troubled electricians since 1854
| Prof. Pupin's work is OF. popular interest.
1naSmuch as 1t demonstrates the practical
| oility of long-distance cable TELEPHONY and
| in the laboratory of electro-mechanics of
| Columbia University there is an artificial
cable 25O miles in length, over which 1t is
possible to use "a telephone without the
| slightest difficulty. When it is remember
ed that forty miles is considered the great
est length of cable it is possible to use in
| telephone practice, one can appreciate the
improvements that DR.. Pupiu,s method
VIII occasion. 1t is also applicable to air
| wires and will serve to increase the lin
It's OF long distance conversation, as we'll
! as TO diminish the cost of the line wire
which at present must be composed of cop
| per OF large size and is, therefore costly.
| Inc new scheme will be of great advan-
| tage with submarine cal Ies, which at pres
emf can only be worked at very low rates
OF speed and are entirely unsuitable for
telephony.
The investigations which has resulted in
tne solution of these problems was under
taken 90 devise a non-uniform conductor
| Tor electrical waves having the properties
| OF a perfectly uniform CONDUCTOR. In the
| transmission of electrical energy over
conducting wires where the distance be-
tween the receiving and transmitting
| point is sufficiently great such as is the
case in long distance telephoning and
| telegraphy, we have wave transmission
| IN which the term electrical wave implies
| that the energy which at any moment il
! stored up in the medium surrounding the
transmission line is distributed periodic
| ally over the line Now these electrical
| waves which are sent out from the trans
| hitting apparatus have a certain wave
| length, which In the case OF an impressed
| electromotive force with a frequency Of
oOo vibrations second would be about
| eighteen miles. The waves travelling out
| from their source gradually lost their
energy, ana as they proceed along the line
| the amplitude Of both current and poten
| tial becomes less. This Prof. Pupin
terms attenuation, and by a mathematic-
| al treatment Of the subject he has aseer-
tanned that it depends on the inductance
| and capacity of the conductor over which
the waves are passing. This method is TO
| increase the inductance of the circuit
| and theory and experiment show that the
effect Is the same as increasing the con-
| ductivity of the transmission wire The
| increase in the inductance of the circuit Is
particularly useful in telephoning. as
the waves Of lighter frequencies are at
tenuated more than those vibrating less
/ rapidly If the electrical waves on a teIe-
| phone conductor corresponding to the vi
bratfons of the human voice are uneven
| ly attenuated the voice is conseouentIv
| distorted and what is termed defective
| articulation results.
Such difficulties caused by the attenua-
ton of the waves have long been expert
| enced, and the deficiencies of the Atlantis
cable for rapid work were early prophe-
sled by Sir William Thompson dn a math-
ematical paper. Oliver Heavyside OF
| England. the well known mathematic
| physicist, pronounced a theory favoring
the use of wave conductors of high fndllct-
ance, but while this was sa tlsfactory for
q afh ar1a teal III
| dicate how such conductor could be con-
| structed. and none of the experiments 10
determine this fact was successful Prof
Pupin became interested in this question
some years ago and first attacked the
| problem from a mathema teal point of
view, reaching solution which he he's
| since verified by extensive experimental
| ton. He found that if nductance coils
are introduced along the line at intervals
determined by formula the result would
| be to diminish the attenuation Of 5fiit
waves and to increase the current Hav-
| Ing reached this ma thematical solution
DR.. Pupin proceeded to perform a series
of experiments which have shown a re-
markable coincidence in Their. results wit h
| those obtained by purely theoretical con-
| siderations. For the study of these long
| waves he first required a conductor of
great length and capacity, such as cable.
| This was obtained by the construction
| Vi a cOuQtHSeT Oh original QfSlRn, where
| on parafined paper were placed pieces of
tin foil, arranged so as to possess the
| greatest possible length and thus have a
| certain amount of resistance. A number
of these conductors could be connected in
series, and an accurate initial ton of a ca
BILE was achieved, the condensers being so
made as to possess a resistance and ca
| pacity equivalent to that of an actual
| cable. The construction of these cables
| and other parts of the apparatus which
was done for the most part by, Prof
| Pupins students and mechanic5an, was a
task of no little magnitude and during the
| time occupied in the research three sep
| arate cables were made. For purpose Of
study the cables are subdivided into
| lengths of one mile, and at these inter-
walls the inductance cords can be intro
duced or cut out of circuit by the mere
insertion of plug. These cords are about
five inches In diameter and have an H.
ductance of .05S henry, two cords being
wound on the same support.
with such a cable line as a base TO
work on. Prof. Pupin then began the