John Frederick William Herschel to Faraday   31 May 1826

May 31. 1826.

Dear Sir,

My note was merely conversational, nor had I at the time of writing it the slightest idea of in any way appending my own crude notions to a finished production like your paper¹. I wrote merely to clarify my ideas, and I ought rather to apologise to you for making you accessory to such a process, than to wish to see it in print. There is the less need of this as the comment is one which most of your readers will easily make for themselves[.]

With regard to the light of Mr Drummond’s lamp². It is very true that lime colours flame red (Brick-red) - It is true that the general tint of Mr. Drummond’s lamp seen after an oil lamp or after Candle light - verges to greenish or bluish[.] But if we examine the ruddy flame of alcohol containing Prussiate of lime in solution, we shall find it in the green line which distinguishes the light of the ball - only the red line in its Spectrum is far more prominent[.]

The relation of the two lights may be represented thus the Black line represents the lines whose ordinate is proportional to the intensity of the light in different points of the Spectrum in the light of the ball - the dotted line is the flame-light[.]

I remain dear Sir | Yours very truly | J.F.W. Herschel