Phenix gazette. [volume] (Alexandria [D.C.]) 1825-1833, 1826-03-09
For tie Picnic Gazette.
VARIATION OF THE COMPASS

ca Hypothetical reasoning, lis variation has &C.
casioned more inquiry among philosophers than
The original phenomenon OF the cause OF mag
neiic attraction
The British Board of Admiralty, (who have
always appeared anxious for the promotion OF
science) at one time gave orders to all the cap
,ains and masters sailing under their flag, to
keen an exact account of al the variations OF
the compass, which might take place in all
parts of the world, to which they sailed No
ting particularly the latitude and longitude OF
the places in which the variations took place,
together with their bearings, from continents,
islands, SC. Curiosity was long on the tip
Toe, for the result Of this investigation, and the
differences that might be drawn thcrefrom. But
when comparison Of the result came to be
made, they appeared so strange and contradic-
tory, The one to the other, that little informa-
ton was gained therefrom. In some few points,
indeed, they have bore more the stamp OF uni
formity than in others. For instance, IN high
latitudes and cold seasons, the variations were
generally, though not always, towards CONT
nents. In low ATTITUDES and warm seasons, it
was more frequently the reverse; though this
seemed in great measure to depend on the
nature Of the soil and quantity Of mineral con-
tanned in the adjacent continent; AS you ap-
proach the poles, the variation was considera-
bly, greater, so much so, that the needle would
in places poin, almost East or West, while in
other parts of the arctic region, in the same
latitude, but different longitude, it would point
directly to the pole. In one thing it was COM
pletely uniform-as you approached the pole,
the dip of the needle increased in very great
degree.
From the result Of all these experiments and
numerous others, was at one time, led TO be-
Geye. that cold was the cause Of magnetism.
The attraction of the needle TO the main land,
(which is always colder in winter, and warmer
in summer than the ocean, in cold seasons, and
its frequent repulsion in warm, strengthened
the belief; as did its greater variation and dip
in high latitudes. Yetplausible as this theory
at first appeared, it was oyerthrown by the
circumstance, that in the same country the
needle will keep varing gradually Tor certain
number Of years in one direction, till it comes
TO a certain point, E or w when it will as gra-
dually vary in the other direction, till it arrives
at the same number Of degrees from due north
line, while in country few thousand miles L
or w. Of us, in the same latitude, its variations
will be exactly the reverse Of ours.
Hidden and inexplicable as this mystery may
appear there is one plausible hypothesis by
which it may be accounted for:--Though then,
we must drop the Ne,cionian and take the Sym
monian philosophy for our guide. Suppose
the earth to be "hollow concentric sphere,
containing within itself a globe, likewise ho-
low:-Suppose this inner globe to have on the
verge Of its polar opening, one or more very
high eminences Of solid loadstone, or some
other magnetic substance:-and suppose again,
that this inner globe turns on It's axis, indie
pendent Of the outer globe, The magnetism
in the eminence on the inner verge, will carry
round with it the mariners needle till it per-
forms the quarter Of an evolution, or till the
magnetic eminence is farthest Z. or w. from
us, then it will recede, pass the pole, and keep
on till i, is at the opposite extremity BY this
course the needle viii point twice to the pole,
to where it does once to either of the extremi-
ties-and from a long course Of observations
on the variations Of the compass, find this
to be The case True we have 10 make three
suggestions to account for it, yet this is bur one
more than what is made in working the rule Of
Double Position, which invariably produces the
true result.
What peculiar arrangement OF particles
there is in the iron ore called load stone, which
makes it attract the needle, will not pretend to
define: nor can it be accounted for ill the science
Of optics is brought to greater perfec,ion-ye,
will venture to affirm, that the, variation Of
this needle can be accounted for in no other sa-
iisfactory. way, than by allowing the existence OF