Faraday to James Timmins Chance   23 August 1860

[Royal Institution embossed letterhead] | Thursday 23 Aug. 1860

My dear Sir

Let me ask you on one or two points - which I have omitted to note[.]

[1] the distance in the fitting room to the first test place? [14 yards]¹ do. to the extreme test place [22 yards (= 66 feet)]

[2] the distance in the yard to the first observing place? [62 yards]

to the furthest observing place? [105 yards]

[3.] height of the focal plane above the burner? [28]mm

[4] the focal point of the upper reflectors either in relation to the burner or the focal plane? [10 mm above focal plane]

[5] Where do your foci cross in relation to the burner or cotton? [see other page (over)]

[6] Do the final diagram &c in rela[tion] to dip, refraction, &c refer to Whitby or only an imaginary case? [They refer to Whitby: viz: apparent dip = 17’ 40” real = 15’ 14”]

Ever Truly Yours | M. Faraday

Sorry to trouble you but my memory lets things slip. MF

Endorsement: Questn: I presume that this question relates to the lower reflectors. My construction of foci (so far as I have at present arrived) is thus