Researches in Magnetic Electricity. 365 
pair of lead* and zinc plates, eight inches single surface of zine, ) 
kept constantly in good action by the sulphate of copper. One 
of these magnets weighing two ounces, with four coils of fine 
wire exterior to three of large, gave a shock which could not be 
endured. The two best magnets of the sixteen, were, one made 
of one hundred fine wires six inches long, and one of five hun- 
dred wires, ten inches long. ‘This last, furnished the most splen- 
did deflagrations, and by far the strongest shocks. Its decompo- 
sing power was very great, for the means used.. One was prepar- 
ed of one thousand wires, and a foot long, but its power was infe- 
tior to that of five hundred wires. This large compound bar was 
ultimately sawed in halves, and each half indicated as much power 
asthe whole. This fact seems to prove, that the length of the coils 
of copper wire, was too great for the size. I apprehend that a cop- 
per wire of a larger size,} would have made it superior to the other 
Magnets. ‘The advantage before alluded to, possessed by the mag- 
hets prepared from bundles of fine wire, is, the facility of making 
a curved or U magnet,{ wound accurately throughout its length. 
There is little or no advantage in winding common magnets on 
the curved portion, owing to the difficulty of laying the wire on 
that part, at right angles to the axis of the bar. A very perfect 
U magnet covered accurately throughout its length, is readily 
made, by winding a straight bundle of fine iron wire, with as 
Many coils of copper wire as desired, and bending them afterward, 
‘hey are bent with ease, and the wire disposes itself on the bent 
Portion in a beautiful and regular manner. All the magnets that 
Were made of this description, were tried before and after,they were 
bent, and no change in their properties could be observed. The 
est of the magnets, above alluded to, was covered with two 
hundred feet of fine wire, exterior to four coils of large wire. 
Combining the secondary currents of the large and small wire, 
“If properly prepared, lead for the negative plate, is much superior to copper, 
Where the sulphate of copper is used. 
t Thave universally found that large wire answers best for large magnets, and 
small wire for small magnets. The larger the wire, the more freely it conducts, 
but large wire cannot be used with advantage on small magnets, as the coils or 
turns will not be sufficient in number, and the axis of the wire will lie more ob- 
lique to the axis of the magnet, than that of a smaller wire, or than upon a larger 
z t The term, horse shoe, applied to magnets, is inappropriate, and has led many 
into the error of constructing magnets of this awkward and disadvantageous form, 
The letter U would briefly designate this species of magnet. 
