104 
MR. BARLOW ON THE PROBABLE ELECTRIC ORIGIN 
assuming the magnetism of the needle to be due to an infinite number of gal- 
vanic currents parallel to each other and at right angles to the axis, the action 
of needles on each other, of these on galvanic currents, these currents on each 
other, and of the earth itself on each, were all reduced to one general principle, 
admitting of accurate and determinate calculation. 
The view which I had taken of the subject was more limited. Having ob- 
tained a law which expressed a particular class of these phenomena, I pro- 
ceeded no further; but it was satisfactory to me to find, that as far as these 
extended, the expressions were identical, and that all the observed phenomena 
due to every variety of experiment were equally explicable on the one or the 
other hypothesis. It will not be necessary to enter further into the many beau- 
tiful effects which were obtained by the various arrangements of different gal- 
vanic conductors. I shall therefore proceed at once to describe the Experi- 
ment alluded to in the head of this article, which is intended, if not to prove, 
at least to show the high degree of probability, that all terrestrial magnetic 
phenomena are due only to electricity, and that magnetism, as a distinct 
quality, has no real existence. 
Having, as stated in the preceding part of this paper, discovered that the 
magnetic power of an iron sphere resides only on its surface; having also 
shown that when we suppose the earth’s magnetism to vanish, the fundamental 
laws of terrestrial magnetism are exhibited by this superficial action, — the re- 
sulting expressions being identical with those obtained by M. Biot for the 
earth ; it occurred to me, by a very natural induction, that if I could distri- 
bute over the surface of an artificial globe a series of galvanic currents, in such 
a way that their tangential power should every where give a corresponding 
direction to the needle, — such a globe ought to exhibit, while under electrical 
induction, all the magnetic phenomena of the earth upon a needle freely sus- 
pended above it, the needle itself being neutralized from the earth’s mag- 
netism, so as to leave it wholly under the influence of this superficial action. 
This idea was put to the test of experiment as follows. 
I procured a wooden globe sixteen inches in diameter, which was made 
hollow for the purpose of reducing its weight ; and while still in the lathe, 
grooves were cut to represent an equator, and parallels of latitudes at every 
each way from the equator to the poles ; these grooves were about one 
