Royal Observatory Greenwich | 1847 May 19
My dear Sir
We trouble you as a universal referee or character-counsel on all matters of science:- and moreover Sheepshanks1 has troubled you on this matter before2:- and it is very bad but what else can we do? So throwing myself on your justice or mercy, I will proceed to the business.
We must definitely select a metal for the bar-standard of length. And what is most durable? I incline to hard gun-metal (I cannot at this moment give you the proportions that we have tried, but a very white mixture was found very strong, broke with difficulty, did not bend first, and appeared not likely to oxidate). Sheepshanks has set his heart on a pure metal, believing theoretically (I think) that it is not likely to alter internally.
Now can you help us?
Yours very truly | G.B. Airy
Michael Faraday Esq | &c &c &c
Please cite as “Faraday1990,” in Ɛpsilon: The Michael Faraday Collection accessed on 4 May 2024, https://epsilon.ac.uk/view/faraday/letters/Faraday1990