Public ledger. [volume] (Memphis, Tenn.) 1865-1893, 1878-06-10
Edlson'. wonderful rnermopile.


New York Herald. June 4th.I
MIR. Edison explained the instru-
ment to the Herald reporter in the
following words: "It consists Of a
carbon button placed between two
metallic plates. A current Of cleo
tricity is passed through one plate,
then through the carbon and
through the other plate. A piece
of hard rubber or Of gelatine is so
supported as to press against these
plates. The whole is then placed
in connection with a galvanometer
and an electric battery. Heat
causes the strip of hard rubber to
expand and press the plates closer
together on the carbon, allows
more current to pass through and
defects the needle of the galvano-
meter. Cold decreases the pressure.
Moisture near the strip Of gelatine
can be measured in the same way
by increasing or decreasing the pres
sure and accordingly DETECTING the
needle. By means of this appara-
tus or one combined with sensitive
electrical galvanometers it is posi-
BILE to measure the millionth part of
a degree Fahrenheit. Infinitesimal
changes in the moisture of the at
mosphere can be indicated in the
same way-changes which are a
hundred thousand times less in
quantity than those that can be in
dicated by the present barometer.
1t will thus foretell a storm much
more readily. The carbon button
| have in this instrument is of lamp.
black burned from rigolene.
II discovered about two years
ago that carbon of various forms
such as plumbago, graphite, ga
retort carbon and lampblack, whsr
nodded in buttons, decreased tn,
resistance to the passage of th,
electrical current by pressure. Thi
is part Of the apparatus Of the car
bon telephone and microphone
The Washington Star, on Apri
10th, published this discovery, anC
| sent twenty copies of the paper tC
foreign countries, one of them tC
Mr.. w. II. Preece, chief of the
Postal Telegraph Department in
London. have corresponded with
Mr.. Preece and kept him posted
Professor D. E. Hughes, of Eng
land, now claims to have invented
the telephone, microphone and
thermopile. At that time Mr.
Preece had in bis possession tele,
| phones exactly similar to thatwhicl
Mr.. Hughes sets forth as his. Mr.
Preece was also present in this
country, where | showed him the
increase and decrease of pressure by
the thermopile, In June, 1877, an
account Of my discovery appeared
in the Journal of Telegraphy."
Mr.. Edison has sent the follow
ing cable dispatch concerning the
matter to London: i-f5s.
Preece, London: / regard Hughes
heat measure and direct impact
telephone as an abuse of confidence
| sent you and others papers des.
cribing it, also in letters about
trouble with expansion telephones
If you do not set it right l shall,
with details, EDISON.
Sir William Thompson, Academy
Of Science, London: Carbon tele-
phones sent Preece two months
ago; also particulars and letters de,
scribing it as best measure. Great
abuse confidence hispart in Hughes
matter. Await particulars with
proofs. EDISON.
The instrument is CONSTRUCTED
for measuring to an astonishing ex-
actness the lowest degree of heat.
Indeed, if the experiments made
by Mr.. Edison last night prove any.
thing, they show that he has Do
yiSed an instrument go sensitive as
to open an entirely new field in the
realm Of scientific research.