magnetic phenomena produced by electricity. 11 
site to those below, and those arranged vertically on one side, 
opposite to those arranged vertically on the other side. 
I found that contact of the steel needles was not necessary, 
and that the effect was produced instantaneously by the mere 
juxta-position of the needle in a transverse direction, and that 
through very thick plates of glass : and a needle that had 
been placed in a transverse direction to the wire merely for 
an instant, was found as powerful a magnet as one that had 
been long in communication with it. 
I placed some silver wire of ~ of an inch and some of in 
different parts of the voltaic circuit when it was completed, 
and shook some steel filings on a glass plate above them : the 
steel filings arranged themselves in right lines always at right 
angles to the axis of the wire ; the effect was observed, though 
feebly, at the distance of a quarter of an inch above the thin 
wire, and the arrangement in lines was nearly to the same 
length on each side of the wire. 
I ascertained by several experiments, that the effect was 
proportional to the quantity of electricity passing through a 
given space, without any relation to the metal transmitting 
it : thus, the finer the wires the stronger their magnetism. 
A zinc plate of a foot long and six inches wide arranged with 
a copper plate on each side, was connected, by a very fine 
wire of platinum, according to your method ; and the plates 
were plunged an inch deep in diluted nitric acid. The wire 
did not sensibly attract fine steel filings. When they were 
plunged two inches, the effect was sensible ; and it increased 
with the quantity of immersion. Two arrangements of this 
kind acted more powerfully than one ; but when the two 
were combined so as to make the zinc and copper-plates but 
