The Saint Paul globe., 1897-10-31

ence, Prof. Bigelow's researches, re-
| sulting now in this interesting story,
| have been in progress at the weather
| bureau building for number of years,
and are still being carried on. His
deductions have been drawn from data
| furnished him by all of the important
| magnetic observatories which exist
about fifty in all-distributed over both
| the northern and southern hemi-
| spheres.
| MAGNETIC NEEDLES DISTURB
ANCES.
For many years magnetic observers
! have noticed that on certain days the
| magnetic needle suffers great variation
| and disturbance. For instance, if the
needles at a given moment are pointed
in certain directions at the several sta
tions, they will all suddenly tilt up
ward and stand more nearly perpan-
| dicular. This is due to the strength
| ening of what is called the external
| magnetic field surrounding the earth.
| Such changes come at irregular inter
vals and are spasmodic. Further
more, there are other impulses which
| move the magnetic needle back and
lOGln through CSI ldIl NSli-oCAiICu ~
| riodic curves.
All of these effects, in Prof Bige-
lows opinion, depend upon sources
outside the earth. In the observatories
cooperating with him, instruments OF
precision have measured and recorded
the directions and forces of these i'm
pulses, both horizontally and vertical
ly. The records of the instruments
have been reduced to tables and dia-
grams from which the new theory
has been deduced.
Prof BigelCw believes that the suns
tremendous magnetic force, flowing in
upon US, is turned out Of it's course
on reaching the earth'S surface. 1t
does not appear to penetrate the en-
tire body of the earth, but to permeate
only a comparatively thin shell on the
outside, as suggested. It appears as
though the magnetic force, coming
thus from the outside, were trying
to avoid large nucleus inside the
earth, but readily permeating the up
per layers Of the crust.
A SIMPLE ILLUSTRATION.
Suppose said Prof. Bigelow, "that
you have ball fixed in a stream of
water. The lines of flow will pass
]
respond to some extent with these
magnetic lines. The outer shell of the
earth seems to gather the magnetic
rays into itself, like a piece of soft
iron, because it is a better conductor
of the magnetic force than is the sur
rounding ether. One system of the de-
f1ecting rays in the northern hemis-
phere points toward the sum- and in the
southern hemisphere away from the
sun, as if trying to turn the earth so
that the northern hemisphere should
point more directly toward the sun.
Furthermore, the angles at which these
rays touch the surface of the earth in
dicate that they are refracted like rays
Of light entering a surface of glass.
Another system of forces shows that
the north pole of the sun is, in all
probability, positive, and the south
pole, negative. These other rays, COM
ing from the sun, become concentrated
in two belts, upon the earth, one on the
northern and the other on the southern
hemisphere. The northernmost forms
a rude oval around the magnetic and
geographic north poles of the earth
and constitutes the area within which
the auroras are observed.
DEDUCTION FROM THESE PHE-
NOMENA.
'It is we'll known that the auroras
are less frequent near the North pole,
that they are most frequent at from
eighteen to twenty degrees below it,
and that they fall off to the minimum,
southwark 1t is also known that the
years in which the auroras are most
frequently seen correspond exactly with
those in which are observed the great
est number of sun spots, as we'll as with
the years when the greatest disturb
ances have been detected in the mag
netic field of the earth. These three
phenomena have persisted so long in
acting together as to leave no doubt