Faraday as a Discoverer | Page 9

i. p. 338 et seq.
[2] Paris: Life of Davy, p. 391.
[3] Viz., November 19, December 3 and 10.
[4] I make the following extract from a letter from Sir John Herschel,
written to me from Collingwood, on the 3rd of November, 1867:--
'I will take this opportunity to mention that I believe myself to have
originated the suggestion of the employment of borate of lead for
optical purposes. It was somewhere in the year 1822, as well as I can
recollect, that I mentioned it to Sir James (then Mr.) South; and, in
consequence, the trial was made in his laboratory in Blackman Street,
by precipitating and working a large quantity of borate of lead, and
fusing it under a muffle in a porcelain evaporating dish. A very limpid
(though slightly yellow) glass resulted, the refractive index 1.866!
(which you will find set down in my table of refractive indices in my
article "Light," Encyclopaedia Metropolitana). It was, however, too soft
for optical use as an object-glass. This Faraday overcame, at least to a
considerable degree, by the introduction of silica.'
[5] Regarding Anderson, Faraday writes thus in 1845:--'I cannot resist
the occasion that is thus offered to me of mentioning the name of Mr.
Anderson, who came to me as an assistant in the glass experiments, and
has remained ever since in the laboratory of the Royal Institution. He
assisted me in all the researches into which I have entered since that
time; and to his care, steadiness, exactitude, and faithfulness in the
performance of all that has been committed to his charge, I am much
indebted.--M. F.' (Exp. Researches, vol. iii. p. 3, footnote.)

Chapter 3

.
Discovery of Magneto-electricity: Explanation of Argo's magnetism of
rotation: Terrestrial magneto-electric induction: The extra current.
The work thus referred to, though sufficient of itself to secure no mean
scientific reputation, forms but the vestibule of Faraday's achievements.
He had been engaged within these walls for eighteen years. During part
of the time he had drunk in knowledge from Davy, and during the
remainder he continually exercised his capacity for independent inquiry.
In 1831 we have him at the climax of his intellectual strength, forty
years of age, stored with knowledge and full of original power.
Through reading, lecturing, and experimenting, he had become
thoroughly familiar with electrical science: he saw where light was
needed and expansion possible. The phenomena of ordinary electric
induction belonged, as it were, to the alphabet of his knowledge: he
knew that under ordinary circumstances the presence of an electrified
body was sufficient to excite, by induction, an unelectrified body. He
knew that the wire which carried an electric current was an electrified
body, and still that all attempts had failed to make it excite in other
wires a state similar to its own.
What was the reason of this failure? Faraday never could work from the
experiments of others, however clearly described. He knew well that
from every experiment issues a kind of radiation, luminous in different
degrees to different minds, and he hardly trusted himself to reason upon
an experiment that he had not seen. In the autumn of 1831 he began to
repeat the experiments with electric currents, which, up to that time,
had produced no positive result. And here, for the sake of younger
inquirers, if not for the sake of us all, it is worth while to dwell for a
moment on a power which Faraday possessed in an extraordinary
degree. He united vast strength with perfect flexibility. His momentum
was that of a river, which combines weight and directness with the
ability to yield to the flexures of its bed. The intentness of his vision in
any direction did not apparently diminish his power of perception in
other directions; and when he attacked a subject, expecting results he
had the faculty of keeping his mind alert, so that results different from
those which he expected should not escape him through preoccupation.
He began his experiments 'on the induction of electric currents' by
composing a helix of two insulated wires which were wound side by

side round the same wooden cylinder. One of these wires he connected
with a voltaic battery of ten cells, and the other with a sensitive
galvanometer. When connection with the battery was made, and while
the current flowed, no effect whatever was observed at the
galvanometer. But he never accepted an experimental result, until he
had applied to it the utmost power at his command. He raised his
battery from 10 cells to 120 cells, but without avail. The current flowed
calmly through the battery wire without producing, during its flow, any
sensible result upon the galvanometer.
'During its flow,' and this was the time when an effect was expected--
but here Faraday's power of lateral