George Biddell Airy to Faraday   19 August 1854

Royal Observatory Greenwich | 1854 August 19

My dear Sir

I have some thought of trying pendulum experiment[s] in a mine, as I did (unsuccessfully) a good many years ago¹. At that time I saw R.W. Fox², and he was possessed with the idea that the vibrations of a pendulum might be influenced by magnetic currents in the rocks about it³. I should be very much obliged if you will tell me in the first place whether you think that there can be any such attraction: and if so, of what kind. I may point out what would be the effects of different kinds of force (A) If the force were a steady vertical force, it would be injurious (B) If the force were always opposed to the motion it would not be injurious (C) If the force aided the motion in the approach to perpendicular position, and opposed it in the recess from perpendicular position, it would be injurious. In the second place, would such force be annihilated by destroying the insulation of the pendulum.

I regret to trouble you with what may be foolish questions:- but if there is any reality in the thing it may be important - and to whom else can I go for information?

I am, my dear Sir, | Yours very truly | G.B. Airy

Professor Faraday