James Timmins Chance to Faraday   10 February 1862

Handsworth Birmingham | 10 Feb. 1862

My dear Mr. Faraday,

The only clause of the Specification¹ about which any difficulty arises is the new one No.11, which seems rather long in its present form.

Have you any objection to require adjustments for the sea horizon for all heights: this would simplify the clause, & remove the line of demarcation, (at present indefinite) between heights for wh: an allowance for the dip is not necessary, & those for wh: it is desirable.

It is always as easy for the manufacturers to adjust to the sea-horizon direction, as to the dead level one.

I think that it wd be well to insert the requirement of well polished surfaces, especially for the totally reflecting ones, whose effectiveness depends entirely on their perfect truth of surface.

Would it be not desirable to require that the glass should be adjusted after the framework has been put together, instead of by individual, separate portions?

Mr. Stevenson in his recent specifications introduces this condition.

Also prisms should be of their full size so as not to allow light to escape between them.

Yours very truly | J.T. Chance.

After hearing from you I will send you my notions in a complete form.