n order, if possible, to
forestall the monopolising designs of those who seem to regard this
most interesting subject merely in the light of pecuniary
speculation.' He was naturally led to investigate the laws of
electro-magnetic attractions, and in 1840 he announced the important
principle that the attractive force exerted by two electromagnets, or
by an electro-magnet and a mass of annealed iron, is directly
proportional to the square of the strength of the magnetising current;
while the attraction exerted between, an electro-magnet and the pole
of a permanent steel magnet, varies simply as the strength of the
current. These investigations were conducted independently of, though
a little subsequently to, the celebrated enquiries of Henry, Jacobi,
and Lenz and Jacobi, on the same subject.

On December 17, 1840, Mr. Joule communicated to the Royal Society a
paper on the production of heat by Voltaic electricity. In it he
announced the law that the calorific effects of equal quantities of
transmitted electricity are proportional to the resistance overcome by
the current, whatever may be the length, thickness, shape, or
character of the metal which closes the circuit; and also proportional
to the square of the quantity of transmitted electricity. This is a
law of primary importance. In another paper, presented to, but
declined by, the Royal Society, he confirmed this law by new
experiments, and materially extended it. He also executed experiments
on the heat consequent on the passage of Voltaic electricity through
electrolytes, and found, in all cases, that the heat evolved by the
proper action of any Voltaic current is proportional to the square of
the intensity of that current, multiplied by the resistance to
conduction which it experiences. From this law he deduced a number of
conclusions of the highest importance to electrochemistry.

It was during these enquiries, which are marked throughout by rare
sagacity and originality, that the great idea of establishing
quantitative relations between Mechanical Energy and Heat arose and
assumed definite form in his mind. In 1843 Mr. Joule read before the
meeting of the British Association at Cork a. paper' On the Calorific
Effects of Magneto-Electricity, and on the Mechanical Value of Heat.'
Even at the present day this memoir is tough reading, and at the time
it was written it must have appeared hopelessly entangled. This, I
should think, was the reason why Faraday