Faraday to Isambard Kingdom Brunel   26 December 1848¹

R Institution | 26 Decr. 1848

My dear Brunel

The effect you refer to is one of refraction & there is nothing more beautiful than the examination of the shadow of a flame by a Voltaic or a lime light. I am in the habit of procuring it in the Lecture room 3 or 4 feet in width & yet with extreme precision of form in the striae &c & for by adjusting the distance of the candle between the focal length & the screen so as to have these latter in the relative secondary focii - the effect is very beautiful[.] Only as the middle of the flame is not so hot as an outer coat & yet both are hotter than the surrounding air you have to vary the distance for the perfect refracted image of the one part or the other[.]

Ever Truly Yours | M. Faraday

I.K. Brunell Esq | &c &c &c