e inch, and to keep it suspended;
and the amount of weight it will be capable of suspending will be
the greater the more rapidly the zinc is dissolved.

By alternately interrupting and renewing the contact of the zinc
with the acid, and by very simple mechanical arrangements, we can
give to the iron an upward and downward or a horizontal motion, thus
producing the conditions essential to the motion of any machinery.

This moving force is produced by the oxidation of the zinc; and,
setting aside the name given to the force in this case, we know that
it can be produced in another manner. If we burn the zinc under the
boiler of a steam-engine, consequently in the oxygen of the air
instead of the galvanic pile, we should produce steam, and by it a
certain amount of force. If we should assume, (which, however, is
not proved,) that the quantity of force is unequal in these
cases,--that, for instance, we had obtained double or triple the
amount in the galvanic pile, or that in this mode of generating
force less loss is sustained,--we must still recollect the
equivalents of zinc and coal, and make these elements of our
calculation. According to the experiments of Despretz, 6 pounds
weight of zinc, in combining with oxygen, develops no more heat than
1 pound of coal; consequently, under equal conditions, we can
produce six times the amount of force with a pound of coal as with a
pound of zinc. It is therefore obvious that it would be more
advantageous to employ coal instead of zinc, even if the latter
produced four times as much force in a galvanic pile, as an equal
weight of coal by its combustion under a boiler. Indeed it is highly
probable, that if we burn under the boiler of a steam-engine the
quantity of coal required for smelting the zinc from its ores, we
shall produce far more force than the whole of the zinc so obtained
could originate in any form of apparatus whatever.

Heat, electricity, and magnetism, have a similar relation to each
other as the chemical equivalents of coal, zinc, and oxygen. By a
certain measure of electricity we produce a corresponding proportion
of heat or of magnetic power; we obtain that electricity by chemical
affinity, which in one shape produces heat, in another electricity
or magnetism. A certain amount of affinity produces an equivalent of
electricity in the same manner as, on the other hand, we decompose
equivalents of chemical compounds by a definite measure of
electricity. The magnet