< letterhead, including prizes and awards in International Exhibition, 1862 for instruments made>
(Manufactory, 6, Vine Street.)
London, E. C.
Sep 30 1865
I am obliged for your esteemed favor.
It is intended that the knife-edges should be slid up and down in the undercut slide to allow of different portions of the spectrum being brought into the fields of view. thus <drawing of the knife-edges up and another of them down>
If there is not sufficient adjustment, or play, allowed to permit of this being done, effectually, please to return the instrument and I will have it altered with great pleasure.
Believe me Dear Sir Your Obed Servt
Fox Talbot Eq FRS.