Faraday to James Timmins Chance   1 April 1862

London | Royal Institution | 1 April 1862

My dear Mr. Chance

I saw the Deputy Master¹ yesterday, and after much conversation, in which many practical manufacturing questions arose, left him under the arrangement, that I was to write these questions to you, but that (as I wished) you had better answer directly to him as if they came from him.

The questions concern a revolving red light of the first order, for the S.W end of the island of Guernsey; and the desire is to have the intervals of light and darkness as 1:3 or 1:4 and this by means of a series of holophotal panels. Now as the divergence of the lens beam is about 6° or 7°, twelve lenses in the circle would give nearly these proportions. Then come the questions

Are you prepared to construct a holophotal apparatus of the first order, divided into twelve parts?

Or to suggest, as manufacturers, any other refracting or glass arrangement to obtain the desired effect?

Do you manufacture red glass?- What kind of red glass do you, from experience, believe to be best?- the gold ruby or the copper ruby?

In applying the red glass, do you think, as regards construction and efficacy, the red glass should be used as sheets introduced in the course of the ray after it has left the optic apparatus; i.e. as it goes seaward, or around the flame before the rays have reached the refracting parts &c?- and if around the flame, would the colour & glass stand the heat, supposing the lamp-glasses themselves were red?- Or could the light be coloured by a globe of red glass placed outside the lamp glass?- or any other form of red glass, perhaps of parts framed together?- which globes or frames you would be able to manufacture[.]

Perhaps you can answer these enquiries off hand from your present knowledge. We do not want to give you much trouble, but are uncertain about the power of manufacturing according to the division into twelve parts &c.

The Deputy master wished me to say that he had forgotten to bring away his drawing.

Ever My dear Sir | Yours Truly | M. Faraday

J.T. Chance Esq | &c &c &c

Endorsement: Hanois Light see separate packet