106 
MR. BARLOW ON THE PROBABLE ELECTRIC ORIGIN 
it, neutralized from the effect of the earth’s magnetism, according to the prin- 
ciple I employed in my observations on the daily variation, and described in 
the Philosophical Transactions for 1823 ; by which means it will become en- 
tirely under the superficial galvanic arrangement just described. Conceive 
now the globe to be placed so as to bring London into the zenith ; then, the two 
ends of the conducting wire being connected with the poles of a powerful bat- 
tery*, it will be seen immediately that the needle, which was before indifferent 
to any direction, will have its north end depressed about 70 °, as nearly as the 
eye can judge, which is the actual dip in London ; it will also be directed 
towards the magnetic poles of this globe, thereby also showing a variation of 
about 24° or 25° to W., as is also the case in London. If now we turn the 
globe about on its support, so as to bring to the zenith places equally distant 
with England from the magnetic pole, we shall find the dip remains the same; 
but the variation will continually change, becoming first zero, and then gra- 
dually increasing to the eastward as happens on the earth. If again we turn 
the globe so as to make the pole approach the zenith, the dip will increase, till 
at the pole itself the needle will become perfectly vertical. Making now this 
pole recede, the dip will decrease, till at the equator it vanishes, the needle 
becoming horizontal. Continuing the motion, and approaching the south 
pole, the south end of the needle will be found to dip, increasing continually 
from the equator to the pole, where it becomes again vertical, but reversed as 
regards its vertically at the north pole. 
Nothing can be expected nor desired to represent more exactly on so small 
a scale all the phenomena of terrestrial magnetism, than does this artificial 
globe : besides, we know from the mathematical laws of action which have 
been referred to, that it is not merely an exhibition of effects, but that if we 
could increase our currents indefinitely, every circumstance of dip and direc- 
tion would admit of actual and accurate computation. 
I may therefore, I trust, be allowed to say, that I have proved the existence 
of a force competent to produce all the phenomena of terrestrial magnetism, 
without the aid of any body usually called magnetic, except perhaps it may be 
* My battery consisted of twenty zinc and twenty copper plates, ten inches square : but the expe- 
riment may be shown satisfactorily by Sturgeon’s circular battery with about two feet of copper 
and one of zinc. 
