The Savannah morning news. (Savannah, Ga.) 1900-current, 1901-12-15
COMPASS VARIATIONS.
EARNEST STUDY NOW GIVEN TO
THE SUBJECT.
Government Investigations on a
Broad scaie-Some Early History
of the Discovery of the Idiosyn-
CRASHES of the Needle.


CRASHES of the Needle.
From the New York.
Washington, Nov. 26.-According to
the present plans, the year 1902 win
be made memorable for its progress
in the investigation OF terrestrial mag
netism. All the civilized nations Of the
world are cooperating and the Unit
ed States, through its Coast and Coed
detic Survey. Is doing its full share.
Few branches Of the scientific work Of
the government are more interesting
than this. or have, because of its rela-
ton to land titles. more practical i'm
portance.
The discoverer of the variations Of
the compass is supposed TO have been
no less a person than Christopher CO.
lumbus. Before his day it. was as
sumed that the needle held true to the
pole. A common school history Of the
United States which is at hand states
on its first page OF narrative that the
compass and the astrolabe-an instru-
ment for reckoning latitude-had been
invented, and voyagers were no longer
compelled to creep along the shore,
open sea-" A few pages later the same
| text book records that. to the dismay
Of the sailors on the fleet Of Column
bus, the compass no longer pointed
directly north, and they believed them
selves going into a region where the
very laws of nature were changed"
DR.. Tittman, the superintendent of the
Coast and Geodetic Survey, regards 1t
as rather remarkable and a tribute to
81 n
the party of Columbus happened to dis
cover this error, for il was
not great. When Columbus sailed from
Palos the needle there pointed slight
ly east of north. AS he moved west
ward the amount of the easterly devia-
| ton grew gradually less, till, on Sept.
-, he crossed the so-called agonic line,
or the line of no magnetic declination
| or variation. This lay a little to the
west Of the Fayal Islands. For CEN
/ fury or two. before Columbus time
! the needle had pointed approximately
| TO the true north, or by only a small
| amount east of It, over the entire Med
| iterranean region. Where any varia-
tion had occurred in the needle, the
surveyor assumed that it was due to
! some mechanical defect, and promptly
shifted his compass card. 1t thus APP
/ pears that there had been little occa-
sion to question the trustworthiness of
! the north-seeking needle until Column
bus crossed the agonic line, and a
slight deviating to the westward be-
gan.
It has been popularity explained for
years that the needle pointed to a mag
netic pole, which has. been located at
! spot northwest of Hudsons bay or
Beothia Felix, but recently scientists
have not been so sure of the fixity of
| this magnetic pole. The fluctuations
In the needle from time to time through
secular periods, to say nothing of the
slight variations at different hours of
the day, indicate that many elements
enter into the reckoning, and science
| has by no means settled the cause and
meaning of them all. 1t is easy to
account for local eccentricities Of the
needle by the presence of deposits of
iron or other metals attracting or re-
pelling the needle, but the theory un-
DERIVING the whole thing still remains
much in the dark.
Just now the work OF. this govern
ment, and of most of the others CO.
operating with it, is decidedly practical.
From large number of observations
1t is expected that the reasons for
them VIII eventually reveal them
selves. Our government will soon have
established four magnetic Observable
rtes, besides many temporary places
known as magnetic stations The OBJ
sereatories are situated at Sitka, near
Honolulu, at Baldwin, Kan and at
Cheltenham, Nd, sixteen miles from
this city. The Germans have recently
decided to establish a magnetic OBJ
servatory in the Samoan Islands, and
the present Antarctic explorations have
a direct relation to terrestrial magnet
ism. 1t is expected that they will throw
some light upon the magnetic pole at
the south. about which less has been
known than about the one in our hem
isphere. Magnetic observatories have
been established all over the globe, and
they will begin on Feb. l. 1902, to make
simultaneous magnetic observations on
certain selected days, generally the
first and the fifteenth of each month,
and to continue them for at least one
year. At these observatories, about
forty in number, observations of mag
netic variations will be recorded con-
tinuously by Photographic appliances
Our government is also cooperating
with the land surveyors by issuing to
them charts from time to time showing
the variations of the compass at all
points throughout the country. The
surveyors in return report to the gov
eminent such discrepancies as they dis
cover, and so form a useful adjunct
to the work of the regular magnetic
; |
the form of maps over which isogonic
lines have been traced connecting
places of equal variation of the needle,
on the same principle as the more IA
miliar isothermic lines of the weather
maps; they have to be changed oc-
casionally. but not often enough to
make intelligent surveying very mac
curate. The conclusion one would
reach on looking over the literature Of
the magnetic bureau is that the needle
is of little value. and that for the
obvious convenience in its use we pay
, a large price in trouble and error
Nevertheless, one of the Eastern states
is still so far behind the times as to
recognize on its statute books the mag
netic meridian as the meridian of ref
erence for land-surveyors. In many
. other states no systematic effort has
/ been made to put its land surveying
on a practical and scientific basis, &c
as to save costly and unnecessary liti-
cation in the future.
The total change between the morn
ing and afternoon extremes Is only
about eleven minutes in midsummer
and perhaps half this amount in mid
winter: yet this is a quantity which
must not be ignored in precise work
In Germany, mine surveying has been
brought to such an art that some OF
the principal mines maintain small
magnetic observatories. where the de-