My Dear Sir,
I am this moment favoured with your letter, <1> and am delighted to hear of your troublesome Spectrum which must be something interesting. I have been hard at work on the subject of absorption, and have been fortunate in discovering a fact which proves the connecting link between the phenomena of Interference and those of Absorption. This overturns many favourite views of my own on the subject of absorption as a primary principle, and generalises the views of Newton <2> respecting the colours of Natural bodies. – There are many difficulties, however, to be overcome in establishing his theory, & in explaining the total disappearance of one of the complementary tints; and when this is done the theory necessarily requires a considerable modification.
I do not know if I mentioned to you that I have been engaged in drawing up Memoirs of the Life & Writings of Sir Isaac Newton <3> on a large scale. I have been most kindly promised the use of the Newton MSS in the possession of the Earl of Portsmouth, by Mr Fellowes, and I have engaged to meet him at Hurstbourne Park <4> on the 10th of May to inspect this valuable Collection of Papers. I am therefore most anxious to establish & extend the Newtonian Theory of the colours of Natural bodies, <5> and the more so as I have been one of the Ringleaders in the assault which has been made upon it. <6>
I expect to be about a week in London either on my way to Hurstbourne, or on my return from it, and I look forward with much pleasure to the chance of seeing you.
I am at present drawing up a Treatise on Optics on a large scale for the Encyclopædia Britannica, and as I am anxious to give a full account of recent investigations you would oblige me much if you could give me a memorandum of your various papers and discoveries that I may not commit any [illegible] this omission, which I should run a risk of doing without such an Index.
I have been able to observe the complementary reflected tints in various coloured minerals, or Apical coloured glasses and fluids; but I have failed today in an elaborate attempt to make this observation on the Ammonuret of Copper, in Sulphur, & Sulphate of copper. I wish you try your skill in such an experiment.– What a Spring this has been! It is now snowing as if it were mid Winter, & there is no prospect of getting the Seed into the Ground.
I am My Dear Sir Ever Most Faithfully yrs
D Brewster
Allerly by Melrose
April 12th 1837
Notes:
1. Not traced.
2. Sir Isaac Newton (1642–1727), natural philosopher.
3. D. Brewster, The Life of Sir Isaac Newton (London: John Murray, 1831). [This is distinct from the Memoirs of the Life, Writings, and Discoveries of Sir Isaac Newton (Edinburgh: Thomas Constable & Co., 1855). [See Doc. No: 06921].
4. In Hampshire.
5. Which depended upon the emission (or particle) theory of light.
6. Word omitted.