Public ledger. [volume] (Memphis, Tenn.) 1865-1893, 1877-04-19
TIE TRANSMISSION OF CORRECT
TIME.
Scientific American ]

Scientific Americana
The public clocks in the CITY of
Vienna, Austria, are at present
driven by pneumatic system, ac-
tusted at the Imperial observatory
by an automatic arrangement con-
nected with an astronomical time
piece. The idea originated with
an engineer ernamed E. A. Mayrhope,
who had long experimental with
the transmission Of time by means
Of electricity, and at last gave it up
in favor Of pneumatic transmission,
which is free from the drawbacks
and uncertainties connected with
the use OF electric batteries, insu-
lated wires for transmission, deli
cate contact breakers, and other
complicated arrangements. Such
annoyances have occurred in the
experiments made in this country,
and electric arrangements for the
transmission Of tinh have thus far
never been in use for any consider
able period. Some years ago, a time.
ball in the New York tOm-house,
intended to be regulated by an cleo
trio current from the Dudley OBJ
servatery at Albany, soon failed,
because Of the constant attention
required, which could only be ex-
pected from persons specially en-
gagged and exclusively interested in
electric transmissions. Therefore
it is not to be expected that such
an enterprise can be successful until
telegraph companies take hold of
the matter; and only in such case
is there possibility of a regular
working of electric time-pieces.
The method of Mr.. Mayrhope
consists in originating a wave of
compressed air, which is sent
through alright tubes laid along
the street mains to all the public
clocks. This wave is transmitted
once every minute, when the min
ute hands Of the clocks move for
ward the required distance. 1t is
intended to extend this system until
it includes the clocks in all the
schools, public institutions, hotels,
railroad depots, and the houses of
such persons as desire it.
There is no doubt that this
method has the enormous advan-
tage Of simplicity, especially when
applied to a great number of clocks.
Such q pneumatic tube may have
ever so many branches; and at the
end of every branch the impulse
must invariably reach the moving
lever which, pushed by an elastic
membrane, will propel the minute
hand. 1t must, however, be borne in
mind that, by this system, the clocks
will not move so instantaneously
as the electric current. Electricity
is transmitted over a telegraph wire
with a velocity of from 1000 to
1000 miles per second, according
to the perfection Of the insulation
therefore the motion of the various
clocks will be practically isochro-
nous. But the wave of compressed
air, transmitted by the elasticity
of the atmosphere, moves only with
the velocity Of sound, which is, on an
average, onk HOO feet, or little over
one-fifth Of q mile per second, minus
the resistance in the narrow Tubes,
which may reduce it somewhat; so
that its velocity of transmission
may vary from $4,000 to 10000
times less than that of electricity.
This, however, is Of little practical
importance, as it would only cause
the clocks to be one second be-
hind for every HOO feet distance
from the central station; and if in
some egses seconds had to be count
ed, the correction would be easily
applied. Clocks at d mile distance
would be about five seconds behind,
and the correct amount having been
determined by direct observation, a
constant number would have to be
added to the time indicated by each
clock, in order to find the correct
time to within a fraction of a Sec
ond.
But if we 20 into such close cal