The Portland daily press., 1868-06-12
Variation of the Compass.

Variation of the Compass.
We have received a printed copy of very
interesting paper on terrestrial magnetism,
read before the American Institute by Mr..
John A. Parker of New York. Mr.. Parker
will be remembered by our older citizens as
the former partner in business of the late
Nehemiah Cram. He left Portland nearly
forty years ago. Drawn by strong natural
bent to Investigations quite remote from his
daily avocatioDs, he has for years devoted his
ample leisure to the higher problems of ply
sical science, and in this paper presents some
novel theories which if they shall become es-
tablished will rank among the most daring
and felicitous in the annals of scientific dis
covery.
lie claims in the first place to have discov-
cred the law OF magnetic variation, a law
winch harmonizes the contradictory and con
fused indications of observations in differ
ent parts OF the world and at different dates,
law by which, if it shall. be completely es-
tablished, having given the year and the lati-
tude and the longitude of the place, the va
Ration of the compass may be calculated
with as much precision as the time of sun
rise or sunset tor given day. tits unneces-
sary to enlarge upon the practical worth of
such discovery in navigation and in settling
vexed questions respecting boundary lines
run by compass. The theory is as simple as
the the theory of gravitation. Mr.. Parker
believes that the magnetic pole, the point to
which the needle everywhere ooints, is not
stationary, but revolves about the geograpbi-
cal pole, moving from east to west, in a peri
od OF about $40 years. The variation of the
needle from the true north was first observed
SO far as any record shows, by the Italian
philosopher Peregrini in 1870. Columbus OBJ
served it with considerable alarm during his
first transatlantic voyage in 1892. No ac
curate observations were made for nearly a
century later. The first recorded date is
1916 when in London the variation was IL
degrees .easterly; in 1657-62 it was reduced
to nothing; and then advanced to "a degrees
westerly in 1915, since which time it has been
decreasing. According 10 Mr.. Parker's the
ory the magnetic pole was in 1860 on the
merleian OF London and in 1915 had reach
ed the meridian 90 degrees west of London.
This theory is sustained by the earliest OBJ
servations in New York ia degrees west of
Lcndon) where in 100 the needle pointed
due north, and has since been moving wester-
ly. These observations, if they stood alone,
would establish the motion of the magnetic
pole and approximately determine the rate of
motion. 1t remains now to enter upon the
immense labor of analyzing the mass of OBJ
servations which have recentIy been made in
all parts of the world. BY such an ANALYSIS
Mr.. Parker's theory must be confirmed or
overthrown.
The speculations which follow are much
more daring; we can only state their drift,
without attempting to repeat the authors
reasoning, which is singularly concise and
defes abridgment To begin, he Identifies
the magnetic force with the hitherto un-
known force of gravitation, and hazards the
conjecture that the centrifugal force which
counterbalances the attraction of grayitation
is identical with electricity, and that both are
developed by revolution as'we see in eectri-
cal machines and revolving belts. 1t would
seem then that the magnetic pole of the earth
should be always at the point nearest the sun.
but Mr.. Parker holds that it is the point on
the earth's surface in line from the centre
OF the planet to the great centre about which
the solar system revolves. The period of
GAO years marks the return of the sun. earth
and the great centre to the same relative DO
sltlon, as the phases of the moon mark the
return of the moon, earth and sun TO the
same relative position.
There are some disturbances in the eouato-
rial regions, which Mr.. Parker attributes TO
the suns influence, and he throws out the
suggestion that the durnal variation of the
needle, which is clearly due to the sun, NAV
taken in connection with the earth's rate of
motion around the sun, furnish new data for
the computation of the SUMS distance. An.
other suggestion which is interesting from its
bearing on the correlation of forces, is that
the variation in the intensity of magnetism
winch has been regarded as occasioned by
changes oil temperature may really be the
cause OF these changes. The change in the
climate OF Greenland since the magnetic pole
four hundred years ago was ON the opposite
side OF the north pole, is certainly striking
Mr.. Parker a,so believes that the motion of
the magnetic pole is not circular but spiral
and that the geographical poles have also a
secular change which accounts for some geo
logical phenomena which have been other
wise explained. In word, he lays be lore us
swarm of ingenious conjectures of which
lew may prove sound theories, and
all will prove helpful to thorough
~ equipped investigators. In one or
two places he seems to limp percept-
IDLY, as where he speaks of the velocity of the
electric current in telesra2hy being inappre-
cable, and again where he adduees the exper-
lment showing that hollow globe of iron
has the same influence upon magnet as a
solid globe OF the same dimensions, to prove
that magnetism like gravitation acts directly
as the mass ard. inversely as the square of
the distance. 1t is necessary, as he says him
sell, to leave the complete solution of these
problems to those whose leisure and legiti-
mate pursuits will allow them to follow out
in minute particulars that which he has only
sought to grasp as a whole. r.
The Condition of Farm stock I'M the Unit
ed States.
In the report of the Department of Agri-
culture based on tba rat,,rns to tbo A,,;l a..