Faraday to John Frederick William Herschel   25 April 1826

Royal Institution | April 25 1826

Dear Sir

In consequence of the extreme pressure of business which I have been subjected to for some time past and am still subject to I doubt very much whether I can be at the Glass Committee on Thursday¹[.] I send you therefore the results of some analytical experiments made on the glass of the Pot No. 1 with specimens taken from the top and the bottom[.] I did not think it worth while nor have I had time to examine the other pots[.]

You will see immediately how accordant these results are with the apparent homogeneity of the glass[.] The slight difference which does exist is probably in part due to errors of experiment and perhaps in part to the circumstance of the lower specimen having been taken from the vicinity of the pot from which it may perhaps have gained a little siliceous matter[.]

You will observe that this glass is not as yet equal to Guignand’s² [sic] in density³ or in the proportions of oxide of lead & that it surpasses all the flint glasses that were analysed in the quantity of alkali present[.] There is no reason to suppose that this great quantity of alkali which is half as much more than that contained in some flint glasses is requisite and it may perhaps be usefully replaced by lead[.]

I am dear Sir | Very Truly Yours | M. Faraday

J.F.W. Herschell Esq | &c &c &c

Address: John F.W. Herschel Esq | &c &c | 56 Devonshire Street | Portland Place