William Crane Wilkins to Faraday   12 December 1861

24 Long Acre | 12th Dec 1861

M. Faraday Esquire | &c &c &c

Sir,

Not having been successful in meeting you at the Royal Institution, I take this opportunity of soliciting the favour from you of the undermentioned particulars, which Mr Sautter has requested of me, for some works he has in hand, I trust you will pardon the liberty I have taken in troubling you, and that you will please afford me this information, for which I shall feel exceedingly grateful[.]

I am Sir | Your Most Obedient Servant | W.C. Wilkins

how the focus is placed of the 1st order & 3rd order Dioptric apparatus, to make the perfection either of the upper or lower zones, according to the following works-

1st order apparatus fixed 115 feet above the level of the Sea

3rd order ditto 70 feet above the level of the Sea -