Audubon Republican. [volume] (Audubon, Iowa) 1894-1925, 1899-02-16
A SERIOUS PROBLEM.
THE COMPASS AND THE GROWING
USE OF ELECTRICITY.

USE OF ELECTRICITY.
"A Danger That the Magnetic Needle|
May BE Rendered Practically USE
| less to the Mariner and the Sur
veyor-A Curious Discovery.
Although the invention and introduce
ton of the trolley system Of street rail-
ways have been of inestimable value to,
civilization it has incidentally wrought
some harm here and there Emphasis
was laid on one Of these draw backs to!
| electric traction in the address delivered
by Professor A. w. Rucker at recent
meeting of the British Association For|
the Advancement of Science.
In various parts of the world observa-l
| tories have been established for the pur
| pose Of keeping track of the changes in<
the direction in which the magnetic
needle points. 1t was long ago discov-
cred not only that the compass does not
aim directly at the north pole, but that
the amount Of variation in it's indica4
tions from true north undergoes slow
alterations. Hence it is necessary I'd
mako fresh charts, showing the varia
ton for different parts of the globS
every few years. But in order to ge {
the data for such corrections-of the
highest importance to the surveyor and
mariner-it is requisite that careful OBJ p
servations be made continuously at d
number of widely separated points
Two Of the most famous and hitherto
useful institutions of this class are stu I
ated in Washington, in the grounds oa
the naval observatory and in Toronto! !
The interference of the electric current
that run through the earth and thsI
track of trolley lines which have beei
constructed near these observatories ing
terfere so much with the behavior O.
the Instruments of both places that thu
records now obtained are practically
worthless. And the experts are greatl(
puzzled by the problem of escaping fror.
this vexatious interruption of thei
work. ......
So delicate are the influences which
the magnets in such an observatory ar.
intended to investigate that they can b
| perceived only when the apparatus
most scrupulously guarded. The rooI-
in which they are mounted is undeI}
! ground. Visitors are never admitted Ell
cept under unusual circumstances am
are required to deposit their jackknives
keys and all other metallic objects about
their persons before entering the apar
ment. The magnets, generally bars d
steel not over six inches long, are poise
| ohn hot &c x1I Al
most minute fractions, and telescope
on an adjacent pillar, is used to rea
| the fluctuations, which are too small
be discernible by the unassisted eye.
| tiny mirror, as big as dime, catches
| beam of light more slender than ii
lead in pencil and reflects it away
a sheet of slowly moving photograph
paper, on which permanent record
made. The arrangement of the apparatI
is such that the movement of the ma
net is magniied many times in the re-,
ord, in order to render the changes pc
ceptible.
There arc three sets Of instrument
on duty in such an observatory. Or
swings horizontally, like a mariner
compass. Another dips up and dow
A third is designed to measure the
tensity Of the earth's magnetism, viii
is separate thing from the directii
in which it acts And so sensitive a
they that their readings are apt to
interfered with by exceedingly trivi
causes 1t is customary for the superb
tendent to inscribe on the scroll "Visi
ors admitted" whenever such a brea,
of the regulations is permitted, so th
in the motion Of the magnets SUSPECT,
Of its meaning will be excited in Z
mind of the scientist who afterward
amines the Photographic trace.
In spite of the delicacy of the app
ratus, it may seem surprising to the VI
mind that the passage Of trolley GU
rents at distance of many rods fro
the observatory should be able to affS
the instruments Wtthin. But they
and it is impossible to separate in 4
record the variations produced by gerl
inc changes in terrestrial magnet
from those which are caused by
trolley. Professor Rucker said Fl
days ago: From all parts of the wo$
we hear of observatories ruined
threatened by the invasion Of the ell
trical engineer. Toronto and WashiIY
ton have already succumbed, .Potsdaa
Pare st. Maur, Greenwich and Kew {
besieged, and the issue largely DEEPER
upon whether these great national
servatories can or cannot make Cd
their defense"
Although the practical service
mankind which is rendered by insti
tions Of this class is alone sufficient
justify their maintenance and to Wa
rant alarm as to their future there
other questions involved which poss
profound interest for the philosopH
We know that the earth is a magE
but as yet no one is able to say w
makes it SO. The fundamental secret
terrestrial magnetism has not b
solved. Then, too, there are vari
changes in direction which mark
behavior Of the needle that remain
be explained. What influence is it {
makes the needle swing to and fro
microscopic extent every day? Why
that tho diurnal cuipo ;S uraator