4G 
THE CANTOR LECTURE, 1890. 
was a grand step forward to the discovery that a core of soft iron, sur¬ 
rounded by its own appropriate coil of copper, could be made to act 
not only as a powerful magnet, but as a magnet whose power could be 
turned on or off at will, could be augmented to any desired degree, and 
could be set into action and controlled from a practically unlimited 
distance. 
Fig i. Fig. 2. 
Figs. 1 and 2.—Sturgeon’s First Electro-Magnet. 
The electro-magnet, in the form which can first claim recognition for 
these qualities, was devised by William Sturgeon, and is described by 
him in the paper which he contributed to the “ Proceedings 33 of the 
Society of Arts in 1825, accompanying a set of improved apparatus 
for electro-magnetic experiments. The Society of Arts rewarded 
Sturgeon’s labours by awarding him the silver medal of the Society 
and a premium of thirty guineas. Amongst this set of apparatus are 
two electro-magnets, one of horse-shoe shape (Figs. 1 and 2), and one a 
straight bar (Fig. 3). It will be seen that the former figures represent 
Fig. 3 . 
Fjg. 3.—Sturgeon’s Straight-bar Electro-Magnet. 
