116 
Grove's elements, of which the platina is inches wide, 
and immersed about four inches in nitric acid, in good 
flat porous cells. The quantity of current which the four 
cells cause to circulate through the magnet is generally 
equal to about 130 grains of zinc dissolved in each cell 
per hour. The mode of suspension was by a fibre of silk 
suspended within a glass cylinder, placed on a kind of stool 
above the magnet, which is used in an upright position. 
In making use of a small magnet I found it advantageous 
to experiment on correspondently small pieces of metal, of 
about the size and weight of a fourpenny piece, (or about 
five-eighths of an inch in diameter, and 30 grains in weight. 
I suspended such pieces of metal as were readily pierced, 
by means of a hole drilled through the upper edge, and 
through which a copper wire, one-hundredth part of an 
inch in diameter, was fastened, with a little hook at the 
other end of the wire, to attach it to a ring at the end of 
the silk fibre. 
Such arrangement is abundantly sufficient for the exhi- 
bition of the effects I am about to describe, and indeed 
with it 1 first noticed several phenomena which had escaped 
my attention when using a much larger magnet. 
Most of the experiments I am about to describe were 
well exhibited by another magnet, of which the core was 
only six -eighths of an inch in diameter, and two lbs. 
weight, of the horse shoe form, and having about 30 yards 
of No. 18 wire coiled upon it, and having similar polar 
pieces. This magnet was excited by three small pairs of 
Grove's battery, with circular cells of the ordinary con- 
struction, having platina strips half an inch broad and 
immersed about three inches in nitric acid. 
In submitting the metals — gold, silver, lead, tin, zinc, and 
cadmium, to the action of the magnet when excited by an 
electric current of only moderate force, for instance, when 
