Chapter IV: Scientific Researches: Second Period (3)

In the eighth series, completed in April, 1834, on the “Electricity of the Voltaic Pile,” Faraday had dealt with the question--at that time a topic of excited controversy--of the origin of the electromotive force in a cell, Volta, who knew nothing of the chemical actions, ascribed it to the contact of dissimilar metals, whilst Wollaston, Becquerel, and De la Rive considered it the result of chemical actions. The controversy has long ceased to interest the scientific world; for, with the recognition of the principle of the conservation of energy, it became evident that mere contact cannot provide a continuing supply of energy. It would now be altogether dead but for the survival of a belief in the contact theory on the part of one of the most honoured veterans in science. But in the years 1834 to 1840 it was of absorbing interest. Faraday’s work quietly removed the props which supported the older theory, and it crumbled away. He found that the chemical and electrical effects in the cell were proportional one to the other, and inseparable. He discovered a way of making a cell without any metallic contacts. He showed that without chemical action there was no current produced. But his results were ignored for the time. After six years Faraday reopened the question. Again the admirable summary of Professor Tyndall is drawn upon for the following account:--

The memoir on the “Electricity of the Voltaic Pile,” published
in 1834, appears to have produced but little impression upon
the supporters of the contact theory. These indeed were men
of too great intellectual weight and insight lightly to take
up, or lightly to abandon, a theory. Faraday therefore resumed
the attack in two papers communicated to the Royal Society on
February 6 and March 19, 1840. In these papers he hampered
his antagonists by a crowd of adverse experiments. He hung
difficulty after difficulty about the neck of the contact
theory, until in its efforts to escape from his assaults it so
changed its character as to become a thing totally different
from the theory proposed by Volta. The more persistently it was
defended, however, the more clearly did it show itself to be
a congeries of devices, bearing the stamp of dialectic skill
rather than that of natural truth.

In conclusion, Faraday brought to bear upon it an argument
which, had its full weight and purport been understood at
the time, would have instantly decided the controversy. “The
contact theory,” he urged, “assumes that a force which is able
to overcome powerful resistance, as for instance that of the
conductors, good or bad, through which the current passes,
and that again of the electrolytic action where bodies are
decomposed by it, _can arise out of nothing_; that without
any change in the acting matter, or the consumption of any
generating force, a current shall be produced which shall go
on for ever against a constant resistance, or only be stopped,
as in the voltaic trough, by the ruins which its exertion has
heaped up in its own course. This would indeed be _a creation
of power_, and is like no other force in nature. We have many
processes by which the _form_ of the power may be so changed,
that an apparent _conversion_ of one into the other takes
place. So we can change chemical force into the electric
current, or the current into chemical force. The beautiful
experiments of Seebeck and Peltier show the convertibility of
heat and electricity; and others by Oersted and myself show
the convertibility of electricity and magnetism. _But in no
case, not even in those of the gymnotus and torpedo, is there a
pure creation or a production of power without a corresponding
exhaustion of something to supply it._”

In 1839 Faraday gave five Friday discourses and a course of eight afternoon lectures on the non-metallic elements. In 1840 he gave three Friday discourses and seven lectures on chemical affinity. But in the summer came the serious breakdown alluded to on page 75. He did no experimental work after September 14th, nor indeed for nearly two years. Even then it was only a temporary return to research to investigate the source of the electrification produced by steam in the remarkable experiments of Mr. (afterwards Lord) Armstrong. He proved it to be due to friction. This done, he continued to rest from research until the middle of 1844, though he lectured a little for the Royal Institution. In 1841 he gave the juvenile lectures. In 1842 he gave two Friday discourses, one of them being on the lateral discharge in lightning-rods. He also gave the Christmas lectures on electricity.

[Sidenote: END OF SECOND ACTIVE PERIOD.]

In 1843 he gave three Friday discourses, one of which was on the electricity generated by a jet of steam; and repeated the eight afternoon lectures he had given in 1838. In 1844 he gave eight lectures on heat and two Friday discourses. He also resumed research on the condensation of gases, and vainly tried to liquefy oxygen and hydrogen, though he succeeded with ammonia and nitrous oxide.

During these years of rest he also did a little work for Trinity House, chiefly concerning lighthouses and their ventilation.