THE CANTOR LECTURE, 1890. 
47 
an electro-magnet consisting of a bent iron rod about one foot long and 
half inch in diameter, varnished over and then coiled with a single 
left-handed spiral of stout uncovered copper wire of 18 turns. This 
coil was found appropriate to the particular battery which Sturgeon 
preferred—namely, a single cell containing a spirally enrolled pair of 
zinc and copper plates of large area (about 180 square inches) immersed 
in acid; which cell, having small internal resistance, would yield a large 
quantity of current when connected to a circuit of small resistance. 
The ends of the copper wire were brought out sideways and bent down 
so as to dip into two deep connecting cups, marked z and C, fixed upon 
a wooden stand. These cups, which were of wood, served as supports 
to hold up the electro-magnet, and having mercury in them served also 
to make good electrical connection. In Fig. 2 the magnet is seen side¬ 
ways, supporting a bar of iron, y . The circuit was completed to the 
battery through a connecting wire d , which- could be lifted out of the 
cup 2, so breaking circuit when desired, and allowing the weigdit to 
drop. Sturgeon added in his explanatory remarks that the poles N and 
S of the magnet will be reversed if you wrap the copper wire about 
the rod as a right-handed screw instead of a left-handed one, or, more 
simply, by reversing the connections with the battery, by causing the 
wire that dips into the 2 cup to dip into the c cup, and vice versa. 
This electro-magnet was capable of supporting 9 lbs. when thus 
excited. 
Fig. 8 shows another arrangement to fit on the same stand. This 
arrangement communicates magnetism to hardened steel bars as soon 
as they are put in, and renders soft iron within it magnetic during the 
time of action; it only differs from Figs. 1 and 2 in being straight, and 
thereby allows the steel or iron bars to slide in and out. 
For this piece of apparatus and other adjuncts accompanying it, all 
of which are described in the Society's “ Transactions " for 1825, 
Sturgeon, as already stated, was awarded the Society's silver medal 
and a premium of thirty guineas. The apparatus was deposited in the 
museum of the Society, which therefore might be supposed to be the 
proud possessor of the first electro-magnet ever constructed. Alas! 
for the vanity of human affairs, the Society's museum of apparatus has 
long been dispersed, this priceless relic having been either made over 
to the now defunct Patent Office Museum, or otherwise lost sight of. 1 
*****-##••*. *■*'* 
Sturgeon's first electro-magnet, the core of which, weighing about 7 
ozs., was able to sustain a load of 9 lbs., or about 20 times its own weight. 
At the time it was considered a truly remarkable performance. Its 
single layer of stout copper wire was well adapted to the battery 
employed, a single cell of Sturgeon's own particular construction, hav¬ 
ing a surface of 130 square inches, and therefore of small internal 
resistance. Subsequently, in the hands of Joule, the same electro¬ 
magnet sustained a load of 50 lbs., or about 114 times its own weight. 
1 Alas ! also that the volumes of his “Annals of Electricity”—the monument of industry, which 
Sturgeon presented to the Artillery N.C.O.’s library—were sold, as out of date, in 1884, prior to 
my memoir of Sturgeon being published in the K.A.I. “ Proceedings.” 
There is, hoivever, at Manchester, (discovered by Professor Silvanus Thompson), a fine por¬ 
trait, in oils, of William Sturgeon, which (or a copy of it) the Royal Artillery ought to possess? 
