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.