ries. Anderson continued to be the reverential helper of Faraday and
the faithful servant of this Institution for nearly forty years.[5]

In 1831 Faraday published a paper, 'On a peculiar class of Optical
Deceptions,' to which I believe the beautiful optical toy called the
Chromatrope owes its origin. In the same year he published a paper on
Vibrating Surfaces, in which he solved an acoustical problem which,
though of extreme simplicity when solved, appears to have baffled many
eminent men. The problem was to account for the fact that light bodies,
such as the seed of lycopodium, collected at the vibrating parts of
sounding plates, while sand ran to the nodal lines. Faraday showed that
the light bodies were entangled in the little whirlwinds formed in the
air over the places of vibration, and through which the heavier sand
was readily projected. Faraday's resources as an experimentalist were so
wonderful, and his delight in experiment was so great, that he sometimes
almost ran into excess in this direction. I have heard him say that this
paper on vibrating surfaces was too heavily laden with experiments.

Footnotes to Chapter 2

[1] The reader's attention is directed to the concluding
paragraph of the 'Preface to the Second Edition written in
December, 1869. Also to the Life of Faraday by Dr. Bence
Jones, vol. 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 consi