r 
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he Valley N atur a 
Established January, 1878. 
(NATURE DISCERE MORES.) 
Henry SKaer, PnWisner- 
Volume I. 
SAINT LOUIS, MO., OCTOBER, 1878. 
Number 10. 
An Electrical Globe for the Exhibi- 
tion of Magnetic Declination and 
Inclination . 
BY PROF. RICHARD OWEN, INDIANA STATE 
UNIVERSITY, BLOOMINGTON, IND. 
Having recently constructed a globe encir- 
cled by insulated wire, along which I can 
pass a current of electricity and thereby ex- 
hibit the relation of a magnetic needle to said 
current. 1 subjoin a description of the con- 
struction and utility of such a globe. To 
facilitate the understanding of its construc- 
tion, I annex a diagram of the globe with its 
wire and battery. 
Having demonstrated the fact, as men- 
tioned in a former number, that currents of 
electricity were constantly passing, in this 
portion of our earth's crust, from east to 
west and from south to north, as indicated 
by a delicate galvanometer, I desired to pro- 
duce on an artificial globe a similar effect. 
This can be done (instead of making the 
globe rotate as the earth does, from west to 
east) by coiling the wire from east to west, 
being careful that the east end connects with 
the positive pole of the battery. 
To prevent the wooden globe from split- 
ting, I had it made of some nine or ten pieces 
of seasoned inch plank, well glued together 
and allowed to dry thoroughly before it was 
placed in the turning lathe. The globe may 
be a sphere nine or ten inches in diameter; 
I had it made slightly spheroidal, the calibre 
at the part intended to represent the equator 
being about 1-10 of an inch greater than at 
the poles. Into these latter poles I had two 
pieces of hard wood inserted to serve as axes, 
on which the globe could turn readity, if 
desired, when mounted on its small light 
frame. From latitude 70° north or thereby 
going south I had minute grooves cut, very 
close to each other and extending to about 
latitude 70° south. I then, by the aid of 
strong glue (laid with a brush into the first 
few grooves at the north to keep the wire in 
place) commenced coiling insulated copper 
wire, No. 22, from my right hand over to my 
left, while holding the globe in my lap; with 
the north end from me, and leaving a few 
feet of the beginning wire uncoiled, for in- 
sertion into the battery. I then pressed the 
wire into the glue-laid channels, by means of 
a hard bone handle, until the glue was dry 
enough to hold the wire in position. Thus 
I proceeded, an assistant facing me and turn^ 
ing the globe and laying on glue, while I ran 
out more wire and forced it into the grooves 
with the bone handle, making in all about 
140 or 150 circles of coils. 
The globe was then placed in its frame, 
and the east or right wire inserted into the 
binding screw of the carbon plates, in a bi- 
chromate of potassa battery, while the ter- 
minal or left hand wire connected with the 
zinc or negative pole. 
Using now sensitive magnetic needles 
which oscillated on sewing needles, thrust 
through corks, I set the globe with its north 
end to the north and placed one of these 
small magnetic needles on a block opposite 
the arctic circle. Of course, the needle, 
while the battery was not at work, pointed 
a little east of north (here about 6°) ; but as 
soon as I depressed the zinc into the liquid, 
the magnetic needle was instantly reversed 
and pointed with its marked end to the south 
as indicated in the diagram. This effect 
arises from the law pointed out by Persted, 
that when a so-called current of electricity 
is passing along a wire coiled as a helix or 
solenoid, the needle will point at right angles 
to this current, if the electricity is strong 
enough, but whichever way it points outside 
the coil, the position of the needle will be 
just the reverse when brought inside or even 
opposite the inside coil, at either end. This 
is shown perfectly in my globe, for when the 
needle is presented anywhere within the 
antarctic circle, it is reversed, just as at the 
arctic circle. By placing the needle on the 
top of the globe, the variation or declination 
will be found to be east. By care there can 
be a sinuous line found near the Cast side of 
the globe, all along which line from south of 
the equator, up to the point which may 
represent Sir John Ross' magnetic north 
pole, there will be no variation. This may 
represent the agonic from S. America by the 
W. Indies ; N. Carolina; Cleavelancl, Ohio; 
Hudsons Bay, etc. to the magnetic north 
pole. 
Another agonic or line connecting places of 
no variation, may be traced with care (hold- 
ing the needle in the hand and moving it 
east or west until it points to the true geo- 
graphical north) along a sinuous line on the 
west side of the globe, beginning in a south- 
ern latitude, about where Australia would 
be (if the American agonic be on the east 
side) and following it up we pass Hindoostan 
and enter the Caspian, etc. 
Between these two agonies, namely from 
Austrailia through the Pacific to America, 
the variation is at present east, as laid down 
in Guyot's Map of Physical Geography, or 
any similar exhibit of the variation of the 
needle. But carry the needle to the east of 
the American agonic line and you will find 
it pointing west, say in the latitute of Boston 
and still more so when you reach Labrador. 
Of course all this would be more satisfac- 
torily traced if I had laid down the great 
continents on my wooden globe, as I design 
doing. 
If the frame of the globe is high enough to 
permit the needle to be now placed under 
the globe, the magnet or compass will be 
found to assume the same position which it 
did when placed above. That absolute dir- 
ection however, which to an inhabitant on 
this side of the globe (represented by what 
is now at top) would be eastern variation, 
must necessarily be to an inhabitant on the 
the opposite side of the globe (which we 
AN ELECTRICAL GLOBE FOR THE EXHIBITION OF MAGNETIC DECLINATION AND INCLINATION, 
