The Mankato free press. [volume] (Mankato, Blue Earth County, Minn.) 1879-1924, 1922-12-01
USE OF RADIO IN
Mine DISASTERS
New Plan Is Now Being
Worked Out
LESSEN THE HORRORS
Experiments Now Being Made
BY Federal Bureau With
Good Success
ASSOCIATED Press Dispatch.l

scuers on the surface and SINNERS
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 great electrical
manufacturing concern, in an ex-
perimental mine at Bruceton, Penn
sylvania, already have resulted in a
degree of success.
While these experiments have so
far failed to develope any practical
method of using wireless waves for
underground communication, never
theless, says a publication OF the
Mines Bureau, they indicate clearly
that electromagnetic waves may be
made to travel through solid strata.
in the Bruceton experiments signals
were held distinctly through nifty
feet of COAL strata, although the
audibility fell off rapidly as the dis
lance was increased. The absorpt.
ion of loss of intsnsity with distance
is very great for the short wave
lengths used in these tests. Longer
wave lengths are known to suffer
less absorption and many possibly
be found practically effective under
certain conditions.
Tests Are Interesting
In this connection it is interesting
to note tests conducted by the United
States Bureau of Standards in drop
ing wireless antennae down deep,
unused Oil wells to underlying rock
strata, in order to send the wireless
impulses through the rock instead
is believed, may be he same as pro-
jecting the antennae upward into
the air strata.
The desirability of substituting
the wireless system of communication
flor the present telephone systems
in use in mines is evident in con-
Isfdering that rock fell 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 it is
giving satisfaction in most mines
the Bureau of Mines announcement
continues. Very often the telephone
cannot be depended upon on account
of falls of rock, grounding due to
warn insulation or extreme damp
ness. In the event of a disaster it
frequently happens that the mine
telephone system is put out of com
mission by the agency that causes
the disaster, at the very time when
it is most urgently needed. On this
account the mining industry is in
terested 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 a means of utilizing
wireless methods for this purpose.
What The Eperlments Were
The preliminary experiments con-
sisted first in receiving signals
from without the mine by means of
a receiver located inside the mine,
and second, both sending and re-
ceiving messages underground
through the strata. 1t was found that
With a receiving instrument set at
point 100 feet underground, signals
sent , from station KDKA, of the
Westinghouse, Electric and Manu-
featuring company, at East Pitts
burgh,p 18 miles away, could be
heard distinctly. About 50 feet
from the receiving station used in
tthe mine in this test was a 6-inch
bore hole extending from the sur
face lined with iron pipe and con ,
tanning electric light wires which
extended therefrom through the
mine. The presence Of these wires,
according to the experimenters, evil
IDENTIFY assisted greatly in the re-
ception Of the signals, for when the
receiving set was carried to an
other point in the mine removed
from the wires and tracks the sig
nails were barely audible through
fifty feet of cover The fact that
signals were detected at all, how
ever, even though family, was de-
clared sufficient evidence of trans
mission through ground to encour-
age further experimenting.
In sending waves Underground a
transmitter was used in such
manner as to send out continuous
waves of 200 to 300 metres length.
On account of the limited time at
disposal no attempt was made to
modify the apparatus in such man
ner as to produce waves Of greater
length.
p The Results Attained
. In all experiments the vertical
antennae were found to give better
results. The horizontal antennae
gave practically no reception. A
lOOp III q IL do u0Cu Will
fair results. All these experiments
were tried with a wave length of
200 to 300 metres, except the re-
ception from Kdka, which was $50
metres.
The strata at the experimental
mine lie almost horizontal The
direction of strata, it was said,
may have some influence on the
transmission of radio waves, but
the. present experiments gave no
conclusive evidence on this point
No doubt the degrees of wetness of
the strata influence the transmits
sion of radio waves, 1t was reported.
The mine used is a. comparatively
dry mine, but the overburden is
damp and small stream of water
is continually flowing from the
mine. This overburden consists
chiefly of soil and soft shale. The
underground workings of the mine
follow horizontal five foot vein
of bituminous coal, and the trans
mission and reception inside the
mine followed the course of this
vein.
Details of the experiment are
explained in Serial 2407, which NAV,
be obtained from the bureau of
mines, at Washington.
-