New Ulm review. (New Ulm, Brown County, Minn.) 1892-1961, 1898-12-14
A SERIOUS PROBI1E / i
THE COMPASS AND THE. GROWING
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 introduc-
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 drawbacks to
electric traction in the addressidelivered
by Professor A. W. Rucker at a recent
meeting a0f the British Association For
the Advancement of Science.
} In various parts Of the world .observa-
tories have been established forthe 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 amonnt of variation in its indica-
tons ifrom true north undergoes slow
alterations. Hence it is necessary to
mako fresh CHARTS showing the varia-
tion for different parts of the globe
every few years. But:in order to get
the data. for such corrections-of the
highest Importance to the surveyor and
mariner-it is requisite that careful OBJ.
servations be made continuously at q
number of svidely separated points.
Two of the most famous and hitherto
useful institutions of this class are stu
ated in Washington, in the grounds of
the naval observatory and in Toronto.
The interference of the electric currents
that run through the earth and the
track of trolley lines which have been
constructed near these observatories in
terfere SO much with the behavior of
the instruments of both places that the
records now obtained are practically
worthless And the experts are greatly
puzzled by the problem of escaping from
this vexations interruption of their
work.
So delicate are the influences which
the magnets in such an observatory are
intended to investigate that they can be
perceived only when the apparatus is
most scrupulousiy guarded. The room
in which they are mounted is under
ground. Visitors are never admitted ex-
cept under unusual circumstances and
are required to deposit their jackknives,
keys and all other metallic objects about
their persons before entering the apart
ment. The magnets, generally bars of
steel not over six inches long, are poised
above scale that is graduated to the
most minute fractions. and telescope,
on an adjacent pillar, is used to read
the fluctuations, which are too small to
be discernibie by the unassisted eye. A
tiny mirror, as big as dime, catches a
beam of light more slender than the
lead in pencil and reflects it away to
sheet of slowly moving Photographic
paper, on which permanent record is
! made. The arrangement Of the apparatus
is such that the movement of the mag
net is magnifed many times in the REQ
ord, in order to render the changes per
ceptible.
There are three sets of Instruments
on duty in such an observatory. One
sw;~gs horizontally, like a mariners
compass. Another dips up and down.
A third is designed to measure the in
tensity of the earth's magnetism, which
is separate thing from the direction
in which it acts. And so sensitive are
they that their readings are apt to be
interfered with by exceedingly trivial
causes. 1t is customary for the superin.
tendent to inscribe on the scroll "Visit-
ors admitted, - whenever such breach
of the regulations is permitted, so that
if any abnormal fuctuation is detected
| in the motion of the magnets suspicion
Of its meaning will te excited in the
| mind of the scientist who afterward ex.
amiues the Photographic trace.
In spite of the delicacy of the appa-
ratus. it may seem surprising to the lay
| mind that the passage of trolley cur
| rents at distance of many rods from
| the observatory should be able to affect
| the instruments within But they do,
and it is impossible to separate in the
! record the variations produced BY genu-
inc changes in terrestrial magnetism
| from those which are caused by the
trolley. Professor Rucker said a few
days ago: From all parts of the world
we hear of observatories ruined OF
| threatened by the invasion of the cleo.
trical engineer. Toronto and Washing
ton have already suCCumbed. Potsdam,
Pare St. Maur, Greenwich and Kew are
besieged, and the issue largely depends
upon whether these great national OBJ.
servatories can or cannot make good
! their defense. -
Although the practical service to
| mankind which is rendered by institu-
tions of this class is alone sufficient to
justify their maintenance and to war
rant alarm as to their future, there are
other questions involved which possess
profound interest for the philosopher
| We know that the earth is a magnet,
but as yet no one is able to say what
makes it so. The fundamental secret of
terrestrial magnetism has not been
solved. Then, too there are various
changes in direction which mark the
behavior of the needle that remain tC
be explained. What influence is it that
makes the needle swing to and fro to a
microscopic extent every day: Why is il
that the diurnal swing is greater in
| Voorc Of cnn cpof Oh &Loy, <kor