The evening times. [volume] (Washington, D.C.) 1895-1902, 1901-02-21
TO TALK UNDER The SEA
Prof. Pupin Gives a Demonstration
in Philadelphia.
He Explains His Invention Mt the
Franklin Institutc-The Subject
Shorn of Many of Its Confusing
standardization 4 Cable for
the Telephone Would Be Laid.

PHILADELPHIA. Feb. 21-Prof NJ. I
Pupin gave a description of his telephone
inventions at the franklin Institute last
evening The most formidable technical
feature Of his address was its title.
Electrical Wave Propagation" His in-
trcduetory remarks were particularly in
teresting. showing the simple means by
which an abstruse subject might be made
easy Of comprehension.
Prof. Pupin asserted most positively
that he did not devise the simple mechan-
zeal analOGies to which he referred con-
tinualIy throughout his discourse fer the
purpose of simplifying the subject of elec-
trio wave transmission for his audience,
but that they were made long ago to en-
able himself to grasp and understand the
underlying principles involved in his
ep0ch-narking invention.
That 1t does open a new era of electrical
telegraphy in lesser degree, may be
gathered from his statement that there
are no difficulties of principle now pre-
venting the construction and laying OF
cable capable of transmitting telephone
speech across the oceans greatest stretch.
Prof Pupin admitted that there are
technical difficulties at present existing to
prevent such an achievement. but that
these are no greater than those that con-
frOnted the pioneers in ca bic telegraphy
when they attempted TO lay the first At
lantic cable, half a century ago. This
statement coming from q professor in Co
lUmbia University. and one who has re-
allied a greater Immediate cash value for
his invention than probably any other
electrical or mecka neal inventor in his
tory, a scientist Of recognized standing. is
worthy Of entire acceptance.
Perhaps the simple apparatus he exnib-
tied at the close OF his lecture affords the
best understanding Of what has been here
tofOTe considered one Of the most abstract
subjects IN the whole realm of science.
First he exhibited a rubber tube about
L feet long connected 20 a reciprOcating
shaft driven by an electrical motor This
tube vas allowed 10 lie upon a strip OF
canvas on the lecture--oon hoor. When
thrown into rythmic vibration, Just as IT
would be by the regular backward and
forward movement Of the hand. II was ap-
parent that the siGuous curves thus pro-
CUced il the rubber tube we're much lare-
CT at the end where the movement was
produced than at the far end
These waves. or curves grew gradually
smaller the farther away frCm The source
or movement. He then attached q sim
liar tube in which were placed small lead
shot at intervals OF two inches When
this loaded tube. so 10 speak. was sim
Harry rhythmicaIly moved it was observed
that the curves, or waves were much
more pronounced along the entire length
OF the tube The same number Of shot
placed in groups at q distance Of twelve
inches apart IN another similar tube har
the reverse sffect-that is. failed entirely
TO transmit the curves. even as well as
the plain tube first shown. Tbs mechan-
ical analogy represents his electrical n
yention
An ordinary conductiou dampens out
or absorbs the energy of the electrical
waves il transmits The coils he adds To
the conducting wires have the same ef-
feet as the lead shots do in the rubber
tune They give density. OF mass to the
conductor, which, according 10 The laws
Of electrical transmission. enables the
transmission Of energy in a wonde rfuIiy
better degree
The beauty and practically of the in
yention lies in the adjustment of the size
and disposition of the coils. exactly as in
the case OF the lead shots Il not proper-
y distributed they decrease the wave
transmitting power Of the wire instead of
increasing ii.
Professor PupIn figures that for the
transmission OF the human voice The wave
length Of the electrical current produced
BY the telephone transmitter diaphragm is
JWJ or three milSs long. This wave length
would require eighteen or perhaps twelve
coils per mile, the coils being small and
inexpensive and measuring about two
inches n diameter and four inches long
In cable they would be combined with
the core and its protecting covering. and
this composite cable would then be laid in
the usual manner. Professor Pupfn says
he considers it quite possible to telephone
across the entire continent overland, or
across any Of the oceans by means of suit
able cables eInbodying these principles.