Warren De La Rue to Faraday   16 December 1851

[De La Rue’s embossed heading] | 7 St Mary’s Road | Canonbury | December 16th 1851

My dear Sir

In reference to our conversation, I must inform you that immediately after leaving you I took home the iron core which has been prepared now about a twelvemonth or perhaps more and placed it on the stage of my microscope, and was glad to find that it would answer well. Being desirous, however, that no slight defect should cause the waste of your time, I determined on making the core part of the instrument, so as to ensure steadiness and to avoid its sliding about in screwing up the ends. A little consideration enabled me to decide on the plan, which I drew out before I went to bed and the next morning I placed the drawing in the hands of Mr Ross¹ who pledged himself not to divulge what was in preparation or to allow the core to be seen by his workmen or any other person. Tonight at 9 1/2 o’clock I received back the instrument.

As I conceive it to be very important to get the points as nearly in the same plane as possible with the object to be operated upon so as to enable us to bring them very close and to still have the lines of force in the most favourable direction, I intend taking my instrument to Bunhill row so as to turn up the moveable end high enough in order that the thinnest film of mica may be used instead of glass on some occasion; and also to see if our workmen can make make [sic] microscopic points as at present they look like clumsy fractures of stout wire. Thirdly to see that there is conducting communication from end to end, that is that the wire has not been injured.

I am having constructed 6 holders of glasses so that one experiment may be prepared whilst another is observed; at present I have only one but I have desired that its thickness might be guaged in order that the top surface of the plate in all should be the same height from the stage[.]

As there is a nichols prism P which fits under the stage experiments on polarized light or the change in the properties of crystals with respect to it may be observed with facility.

If there is any other preparation which you would like to have made I will get it done. A contrivance might easily be made by means of a slip of silver to heat the glass plates if you think this provision desirable.

I remain | Yours Very truly | Warren De la Rue

Michael Faraday Esq | &c &c &c