B.—CHEMISTRY. 35 
discovery of electromagnetic induction that gave the new impulse to his 
mind and gave him confidence in the promptings of his imagination. 
What are the facts ? 
Electricity was one of Faraday’s earliest scientific interests. Long 
before he went to Davy he was experimenting with home-made batteries. 
Already in 1816 we get a glimpse of his intuitive belief in the essential 
unity of the forces of nature, which was to influence so greatly the current 
of his researches. His first lecture to the City Philosophical Society was 
on the general properties of matter, and we find him speculating on the 
forces underlying material behaviour and on their inter-relation. ‘ That 
the attraction of aggregation and chemical affinity is actually the same 
as the attraction of gravitation and electrical attraction, I will not 
positively affirm, but I believe they are.’ In 1821, Faraday repeated the 
experiments of Oersted, Arago and Ampére on electro-magnetism and 
discovered the rotation of a wire carrying a current if free to move round a 
magnetic pole. Magnetism had been produced from electricity, and 
Faraday was convinced of the possibility of obtaining electricity from 
magnetism. In 1824 he was experimenting with a magnet in a helix 
connected with a galvanometer, without result, and similar experiments 
were made in 1825 and 1828. Hither the galvanometer was too in- 
sensitive or he failed to notice the momentary deflection when the magnet 
was introduced. On August 29, 1831, the induced current was detected, 
and ten days of decisive experiment culminated in his paper on ‘ The 
Induction of Electric Currents ’ which was to shape the future of electrical 
science and electrical industry. 
To us it is of special interest that on the very day of the discovery, the 
first test Faraday applied, after he had observed the motion of the magnetic 
needle due to the induced current, was to attach platinum wires to the ends 
of the coil and see if he could detect any decomposition in a drop of copper 
sulphate solution. The test was not delicate enough, but we find him 
returning again and again to the chemical power of magneto-electricity 
until on June 11, 1832, he found in bibulous paper moistened with 
potassium iodide and starch the most sensitive means of detecting the 
chemical action of an induced current. A sentence in his letter to 
Richard Phillips on November 29, 1831, describing his discovery of 
electro-magnetic induction shows how his mind was running on the 
problem of conduction in solutions— I believe it will explain perfectly 
the transference of elements between the poles of the pile in decom- 
position.’ 
His new discovery of magneto-electricity raised afresh in Faraday’s 
mind the old and still disputed problem of the identity of electricities from 
different sources, and chemical action was one of the tests he applied 
to its solution. Having shown that common (frictional), voltaic, and 
magneto-electricity all produce similar physiological, magnetic, chemical 
and thermal effects, Faraday, on September 14 and 15, 1832, established 
quantitatively the identical nature of common and voltaic electricity by 
showing that such quantities of these two kinds of electricity as produced 
equal effects on the needle of his galvanometer also liberated equal amounts 
of iodine, as judged by the intensity of the brown stain, when a piece of 
bibulous paper moistened with potassium iodide was placed in the circuit. 
; D2 
