The Indianapolis journal. [volume] (Indianapolis [Ind.]) 1867-1904, 1902-06-15

be released by telegraph from astro-
nomical observatory and the lights flash
on again. The relighting would mark the
exact moment of time. This would re-
quire an attendant. of course, just as the
time ball does, and it would be necessary
for the observer to be watching for the
signal at the prearranged hour. An eX-
tension of the idea includes auxiliary
clock work located at the building on
which the lights are displayed. The
mechanism is made 10 run exactly four
minutes and forty-five seconds, and then
to shut off the lights and connect the teie-
graph apparatus with them so that when
the signal from the observatory comes
they will be turned on again automatically
exactly on the fifth minute. The same
signal which releases the lights Will give
the clock work another start, which will,
in turn, insure the lights being turned of
again in four minutes and forty-fve sec
onds ready for the next signal In this
way signals will be given every five min
utes as long as the lights burn, and any
ordinary error in time can be corrected by
them accurately.
The third plan is much more complete;
in fact, it reproduces, by means of a tele-
graphic relay or repeating instrument. all
of the signals of a great observatory
clock At the Harvard observatory the
relay Connected directly with the clock
beats every two seconds, emitting one
beat before each minute mark is reached,
so that the exact minute may be easily
noted, and II beats before each five-min-
ute mark. Applied to a big bank of lights
this method will cause momentary inter-
ruptions at two-second intervals with a
pause at the end of each minute and a
longer interval at the end of each five
minutes during which times the lights
would burn steadily. In other words, it
repeats exactly, on a tremendous scale.
the working of the big clock at the OBJ
servatory.
FOR LIMITED SERVICE.
1t is this third plan that has been
adopted for the signals at Cambridge. The
bank of lights is not particularly large
here but it is intended to serve compare
lively small territory and TO be a practical
example OF how the new method can be
applied The whole device is Mr.. Gerrish's
and his idea is not that it should be con-
fined to the use of Harvard Observatory
but that il may be employed wherever the
service of an astronomical station to fur
nish accurate time signals is available. He
has suggested that if the Statue of Liberty
in New York harbor were equipped for the
display of time flashes at night 1t might
be made more useful than it has ever been
before. A service similar to that in Cam
bridge is being furnished by private enter
prise in Boston, the time being taken from
the Harvard Observatory.
A special usefulness Of time signals is
to the masters of vessels in the rating
of their chronometers-that is, in deter
mining the rate of gain or loss which the
instruments show each day. In this con-
nection Mr.. Gerrish makes very inter-
esting suggestion of the possible use of
lighthouses not only warning beacons
but as time signals for mariners. Most
of the big lanterns are what are called
fixed white" lights-that is to say, they
are merely powerful points of ilumina-
ton marking either spots of danger or
entrances to harbors. 1t would seem
perfectly feasible to attach time-signal
apparatus to them, using some form OF
electro-mechanical shutter instead OF
electric lights, and thus giving the pass
ing sailor the benefit of the same service
that ship in the harbor would have.
The operation of the light would then not
be very different from the system. which
has been experimental with more or less
on our Atlantic coast, by which the light
house flashes out its government number,
just as the number Of a fire alarm box is
struck the gong in engine house.
The first night time-signals ever at
tempted were those which Mr.. Gerrish
made experiments with in 1889 with a mag
nesium flash similar to what is used in
photography for taking pictures in the
dark. Apparatus was set up at that time
at the meteorological observatory at Blue
Hill on the outskirts of Boston. Every
night the flash was set off at 10 O'Clock
and one observer reported having seen II
from the town of Princeton at Mount
Wachusett, forty-two miles away. The use
of magnesium had some disadvantages
however, and Mr.. Gerrish discontinued his
experiments for the time being, after having
succeeded in proving the superiority OF
some system of time-signals by the use of a
flash of light.