Sir Humphry Davy on the 
H 
These experiments distinctly showed, that magnetism was 
produced whenever concentrated electricity passed through 
space ; but the precise circumstances, or law of its production, 
were not obvious from them. When a magnet is made to 
act on steel filings, these filings arrange themselves in curves 
round the poles, but diverge in right lines ; and in their ad- 
herence to each other form right lines, appearing as spicuia. 
In the attraction of the filings round the wire in the voltaic 
circuit, on the contrary, they form one coherent mass, which 
would probably be perfectly cylindrical were it not for the 
influence of gravity. In first considering the subject, it ap- 
peared to me that there must be as many double poles as 
there could be imagined points of contact round the wire ; 
but when I found the N. and S. poles of a needle uniformly 
attracted by the same quarters of the wire, it appeared to me 
that there must be four principal poles corresponding to these 
four quarters. You, however, pointed out to me that there 
was nothing definite in the poles, and mentioned your idea, 
that the phenomena might be explained, by supposing a kind 
of revolution of magnetism round the axis of the wire, de- 
pending for its direction upon the position of the negative 
and positive sides of the electrical apparatus. 
To gain some light upon this matter, and to ascertain 
correctly the relations of the north and south poles of steel 
magnetized by electricity to the positive and negative state, 
I placed short steel needles round a circle made on paste- 
board, of about two inches and half in diameter, bringing 
them near each other, though not in contact, and fastening 
them to the paste-board by thread, so that they formed the 
sides of a hexagon inscribed within the circle. A wire was 
