Faraday to Peter Henry Berthon   4 February 1857

4 Feby 1857 | Royal Institution W.

Sir

Having examined the red lead which you sent me on the 30th Ultimo¹, I am in a condition to say, that there are no impurities mingled with it as adulteration;- no red oxide or iron, red earth or other of the red substances sometimes added; nor any thing to make weight[.] As a manufactured article red lead varies, so that there is better & worse, independant of the presence of impurities; but of these differences I am not a competent judge: on such points a person is required, well acquainted with the article & accustomed to compare different qualities.

I am Sir | Your Very faithful Servant | M. Faraday

P. Berthon Esqr | &c &c &c