Daily Kennebec journal. [microfilm reel] (Augusta, Me.) 1870-1975, 1922-11-29
HOPE TO USE RADIO
IN MINE DISASTERS


surface and miners entombed IN
mines following fires and explosions.
/ Is a hope held out by the United
States Bureau of Mines, to lessen the
| horrors and losses Of mine disasters.
| Preliminary tests conducted by the
Bureau, with the cooperation of a
great electrical manufacturing con-
| Germ, in an experimental mine at
Bruceton. PENNSYLVANIA. already
| have resulted in degree Of success.
While these experiments have SO
| far failed to develop any practical
method of using wireless waves for
| underground communication, never
| theless, says a publication of the
Mine Bureau, they indicate clearly
| that electromagnetic waves may. be
made to travel through solid strata.
In the Bruceton experiments signals
1 were heard distinctly through fifty
feet Of coal strata, although the audi
bility fell off rapidly as the distance
was increased. The absorption Of
loss of intensity with distance Is very
great for the short wave lengths used
in these tests. Longer wave lengths
are known to suffer less absorption
| and may possibly be found practi-
calIy effective under certain condi-
tions.
In this connection it is interesting
to note tests conducted by the
United States Bureau of Standards in
dropping wireless antennae down
deep, unused oil wells to underlying
rock strata, in order to send the wire
I i,,on oh,
stead Of through the air. The results,
it is believed, may be the same as
projecting the antennae upward into
| the air strata.
The desirability of substituting the
wireless system of communication
for the present telephone systems in
use in mines is evident in consider
ing that a rock fall or explosion, by
breaking wire connections can put
the entire system out of order.
The mine telephone has been per-
fected to such an extent that 1t is
giving satisfaction in most mines
where the wiring is well insulated,
the Bureau Of Mines announcement
continues. Very often the telephone
cannot be depended upon on account
worn insulation or extreme damp
ress. In the event of disaster IL
frequently happens that the mine
telephone system is put out or COM
mission by the agency that causes the
disaster, at the very time when it is
most urgently needed. On this ac-
count the mining industry is inter-
estcd in any kind of telephone system
that can be counted upon in an
emergency. Many requests have been
received by the Bureau OF Mines to
devise means of utilizing wireless
methods for this purpose.
The preliminary experiments con-
sisted first in receiving signals from
without the mine by means of a re-
ceiver located inside the mine, and
second, both sending and receiving
messages underground through the
! strata. 1t was found that with
receiving instrument set at point
100 feet underground, signals sent
from station kDKA, of the WestlnS-
house Electric and Manufacturing
Company. at East Pittsburgh, is
miles away, could be heard distinct
w. About so feet from the receiving
station used in the mine in this test
was a 6-inch bOre-hole extending
from the surface, lined with iron
nine and containing electric light
wires which extended therefrom
through the mine. The presence or
these wires, according to the expert
mentors, evidently assisted greatly in
the reception of the signals, for when
the receiving set was carried to
another point in the mine removed
from wires and tracks the slgnais
were barely audible through fifty
feet of cover. The fact that signals
were detected at all, however, even
though family, was declared SUM-
cient evidence of TRANSMISSION
experimenting.
Tn sending waves underground
transmitter was used in such man
ner as to send out continuous waves
of 200 to 800 metres length. On ac-
count of the limited time at disposal
no attempt was made to modify the
anparatus in such manner as to
produce waves Of greater length.
In all experiments the vertical
antennae were found to give better
results. The horizontal antennae
gave practically no reception. A loop
of single turn was used with fair
results. All these experiments were
tried with wave length of 200 to 800
metres, except the reception from
KDKA, which was $50 metres.
The strata at the experimental
mine lie almost horizontal. The di-
rection of strata, it was said. may
have some influence on the trans
mission of radio waves, but the pres
ent experiments gave no conclusive
evidence on this point. No doubt
| the degree Of wetness of the strata
influence the transmission of radio
waves, it was reported. The mine
used is a comparatively dry mine,
hut. the overburden is damp and
small stream of water is continually
| flowing from the mine. This over
burden consists chiefly Of soil and
soft shalc. The underground work.
ings of the mine follow a horizontal
five-foot vein OF bituminous coal, and
the transmission and reception In
side the mine followed the course Of
| this vein.
Details of the experiments are ex-
plained in Serial 2401, which may be
obtained from the Bureau of Mines, at
I II;