New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1898-09-25
Curious UECOYNRY.

,,oetir,a.ia val,c to civilization it has incl
Gcntaiy wrought some harm here and there
EInpnas. vas Laid OF one f these drawbacks
TO electric traction in the address delivered by
Professor !. ". Rucker At the recent meeting
OF ,hc British Association for the Advancement
of Science
In various parts Of the world obserYatories
haze been established for the purpose 81 Keep
L. tract; of the CHANGES IN the direction in
which Ire magnetic needle points. II was long
aga discovered lot Only that The compass does
moi am directly al the North Pole. but that
tie amount Of variation in its indications from
true n0rth unaorg3es slow alterations. Hence
It is necessary II make fresh charts, showing The
variation for different parts Of the globe every
few years. But in order 10 get The data for
such corrcct)na-of the hishes; importance to
tn surveyor and mariner-t is requisite that
careful observations bc male continuously at "A
number # Udely separated points
Tvy, If the NOS, famous and hitherto useful
institutions Of this class are situated in Wash
ingtou. in thc grounds Of the Naval Ohserva-
tory. ana IN Toronto The interference of the
electric currents that run through the earth ana
the track # tr1ry lines which have been con
strucfr,l near these orscrvatorics interfere so
much with the behavior of the instrumsn ats If
both places that TIE records now obtained are
l
ly puzzled by the problem IF escaping from this
vexatious interruption II their work.
GUARDING TIE APPARATUS.
So delicate are the Influences which the mag
nets in such an observatory are intended 20 in
vestsItc that they can be perceived only wh"h
The apparatus is mos. scrupulously guarded.
The room IN which they are mounted is under
ground. Visitors are never e!mitted except
4
10 deposit their jack knives keys. and all other
neta.lir Dbjcc about their per bef re- IN e.
Ing the apartment. The magnets. generally
bars of steel not over six inches long. ar pois.d
above A scale that is graduated To ID" most
minute fractions. and 4 telescope on an adjacent
pillar. IS us-l - read the fluctuations. which
are too small go bc disccruiblc by ihr uuas-|
sisted eye. \ tiny mirror as blk ls a dime.
catches beam II light more slender than The
lead in a pencil and reflects 10 away 90 2, sheet
Of slowly moving Photographic paper. On which
a permanent record - made Tn arrangement
Of the apparatus Is such that the NOV, incut 81
the magnet is nasnied many times IN n. rec
ord in order to render the changes pcrccptihlc
There ,hroc sets Of Instruments % duty
in such an observatory. one swings horllonial-
~ like a mariners compass Another dips up
and down. third ~ designed to- measure the
intensity ~ n" earth's magnetism. which Is u
separate hing nom the direction IN which II
acts And so sensitive are they hat 'hcr read
inEs are apt 10 be in,crfcrcI with by tx
cccdngly trivial causes II iS customary ior
the superintendent to inscribe On the scroll
"Visiturs admitted" whenever such a breach
Of the regulations is permitted. so that II
any abnormal iluctuaton IS detected in the
motion IF The magnets suspicion Of its mean
ing viii j." excited IN the mind II the scientist
who after" ard examines the Photographic trace
In spite If The deliracy If this apparatus. it
may s"-ra surprising To the lay mind that the
passage # trolley currents at a distance II
many rods from the observatory should Doc able
TO affect the instruments within. But they do
and ii is impossible 20 separate in the record
the variations produced by genuine changes IN
terrestrial magnetism from those which are
caused by the trolley. Professor Fucker said a
few days ago. From all tsrts Of The world we
hear Of obseryajorics ruined or threatened 10y
the invasion Of IN" electrical engineer Toronto
and Washington have already succumhrd. Pots
dam. Pare 81. Maur. Greenwich and Kew ar" be-
siceed. ana The issue largely depends upon
whether these great national Obscrvatorics can
cannot make good their defence"
Although the practical service - mankind
which IS rendered by institutions of this class
is alone sufficient to justify their maintenance
and 70 warrant alarm 20 their future. there
are other questions involved which possess pro-
found interest FOR The philosopher We know
able to say what makes ii so The fundamental
secret IF terrestrial magnetism has not been
solved Then too there are various changes in