James Timmins Chance to Faraday   11 October 1862

Llandudno, N. Wales | 12 St George’s Crescent | Oct: 11.1862

My dear Mr Faraday,

Hanois Light. This morning I had the 4 Knobs, (indicating by 2 strings the height of the burner) permanently fixed in my presence; & the level of top of the burner was marked on one of the standards.

2nd Order Fixed. By memory, I used last the following foci. Lamp 26mm below sea horizon focus.

but I should alter these by experiment for any future apparatus - more like 30 up & 9 to 10 aside, for upper prisms;- and for lower prisms I should like again to examine them.

The French foci (by memory) are:-

Lamp 26mm below horizontal focal plane.

I regret that I am not at home to experiment now

Yours very truly | J.T. Chance