Davy's experiment of fusing substances laid the foundation of the modern
electric furnaces, which are of paramount importance in several great
commercial industries.

While some of the results obtained with Davy's batteries were
practically as satisfactory as could be obtained with modern cell
batteries, the batteries themselves were anything but satisfactory. They
were expensive, required constant care and attention, and, what was more
important from an experimental standpoint at least, were not constant in
their action except for a very limited period of time, the current soon
"running down." Numerous experimenters, therefore, set about devising a
satisfactory battery, and when, in 1836, John Frederick Daniell produced
the cell that bears his name, his invention was epoch-making in the
history of electrical progress. The Royal Society considered it of
sufficient importance to bestow the Copley medal upon the inventor,
whose device is the direct parent of all modern galvanic cells. From the
time of the advent of the Daniell cell experiments in electricity were
rendered comparatively easy. In the mean while, however, another great
discovery was made.

ELECTRICITY AND MAGNETISM

For many years there had been a growing suspicion, amounting in
many instances to belief in the close relationship existing between
electricity and magnetism. Before the winter of 1815, however, it was
a belief that was surmised but not demonstrated. But in that year it
occurred to Jean Christian Oersted, of Denmark, to pass a current of
electricity through a wire held parallel with, but not quite touching, a
suspended magnetic needle. The needle was instantly deflected and swung
out of its position.

"The first experiments in connection with the subject which I am
undertaking to explain," wrote Oersted, "were made during the course
of lectures which I held last winter on electricity and magnetism. From
those experiments it appeared that the magnetic needle could be moved
from its position by means of a galvanic battery--one with a closed
galvanic circuit. Since, however, those experiments were made with an
apparatus of small power, I undertook to repeat and increase them with a
large galvanic battery.

"Let us suppose that the two opposite ends of the galvanic apparatus are
joined by a metal wire. This I shall always call the conductor for
the sake of brevity. Place a rectilinear piece of this conductor in
a horizontal position over an