My Dear Sir,
I have this moment received your interesting letter <1> and in case I may be hurried before I leave this for Hampshire I sit down to answer it immediately.– I am busy drawing up two Papers for the Royal Society, one “ on the connexion between the Phenomena of absorption and those of thin plates <2>” & the other “on the permanent Colours of Natural bodies”. The first I shall forward in the course of ten days.
You once wrote me about the obscure band in the violet space, but I have not seen it, which could only arise from my not having had a bright enough Sun. You mention the triple line g (of course you mean the line b as the most refrangible side of E) and I am happy to be able to enclose a Copy of my drawing of that part of the spectrum which I made in 1832. You will see that it is in perfect harmony with your observations, with this difference that I have seen other more minute lines. The upper part of the Figure is the Solar Spectrum. The under part of the spectrum as altered by Nitrous Gas, from which you have an ocular illustration of the identity or similarity of the action of the Gas, & of the Cause which produces the Solar lines. You say that G3 is a Double line. It is so, but the very faint one is finely exaggerated by the action of the Gas. You would oblige me if you would shew this drawing to the Council of the Royal Society or to Mr Lubbock <3> as a specimen of my labours.
I enclose some oxalate of chromium & Potash which will enable you to verify my observations <4> on the properties of this remarkable substance.
Your expt on the Interference of Light to which you refer, is in my opinion easily explained. The fringes are viewed thro’ the prism BAC, and hence they are increased in number for the reasons which Newton has explained in his Optics <5> (Part I Obs. 1,2,3 and Obs. 24 nos. 1 and last. See also Part II. where the action of the prism is explained).
Your Expt. on the Iodide of Lead <6> is in the highest degree beautiful.– You do wrong in publishing so important an Expt among others. It should have formed a separate article in order to attract the attention whh it merits.
In speaking of the lines of the Spectrum I forgot to mention to you as a delicate test of Instruments, that the double line D has a very fine line between the two.
I have attempted, but in vain to obtain a solution of Mr Bailey’s curious phenomenon. <7> The observation of Bessel <8> is also puzzling.
It will give me great pleasure to point out to you some trains of optical research in which your powers of observation and mathematical acquirements would ensure success.
If it is not too expensive an undertaking I think you should publish the Treatise you mention <9> with coloured plates. Without such plates no person can form an idea of Optical phenomena. I cannot but think that the Sale would defray the expence.
I have long been planning the establishment of a very general Society for making discoveries with the Microscope, the only condition of admission being the obligation to possess a good microscope to be used either by the member or by some other person. In this way a spirit of active observation would be excited, and drawings of curious phenomena might be multiplied & circulated among the Members. I have spoken to some friends about it who highly approve of the scheme. I wish you would turn it over in your mind.
The phenomenon you describe of the luminous patches round microscopic air bubbles is similar to those I have observed in similar bubbles in Glass and Diamond, and Amber, and described in the Geological Transactions.
I am so engrossed with my scientific pursuits that I have done nothing more about Junius, <10> and probably may never find time to pursue the subject.
I leave this on Monday the 8th May, and if you shd not write me before that, you might perhaps write to me at Hurstbourne Park Hampshire. <11>
I am My Dear Sir Ever Most Faithfully yrs
D Brewster
Allerly by Melrose
April 29th 1837
Notes:
1. Not traced.
2. D. Brewster, ‘On the connexion between the phenomena of the absorption of light and the colours of thin plates’, Philosophical Transactions of the Royal Society of London 1837, pp. 245–52. No paper by Brewster on ‘The Permanent Colours of Natural Bodies’ is listed in the Royal Society of London Catalogue of Scientific Papers.
3. Sir John William Lubbock, 3rd Baronet (1803–1865), mathematician & astronomer.
4. See D. Brewster, ‘On certain peculiarities in the double refraction and absorption of light exhibited in the oxalate of Chromium and Potash’, Philosophical Transactions of the Royal Society of London 1835, pp. 91–94.
5. Isaac Newton, Opticks, or A treatise of the reflexions, refractions, inflexions and colours of light… (London: S.Smith & B. Walford, 1704).
6. W. H. F. Talbot, ‘Facts relating to Optical Science, No. IV’, Philosophical Magazine s. 3, v. 9, no. 56, December 1836, pp. 401–407. The article includes observations on ‘The Remarkable Property of the Iodide of Lead’.
7. The unevenness of the edge of light during solar eclipses, a phenomenon also called ‘Baily’s Beads’. It was first observed during an annular eclipse of the sun on 15 May 1836 by Francis Baily (1774–1844), English astronomer. The unevenness of the light was caused by the unevenness of the moons surface.
8. Friedrich Wilhelm Bessel (1784–1846), astronomer, who had been observing Halley’s Comet from Greenwich in 1836. See, Appendix to the Greenwich Observations, 1836: containing No. I. Bessel's refraction tables. No. II. Table of factors for converting errors of right ascension and north polar distance into errors of longitude and ecliptic polar distance (London: 1837).
9. Possibly on the polarising microscope – see Doc. No: 03616.
10. See Doc. No: 03433.
11. Where the Earl of Portsmouth’s collection of the papers of Isaac Newton were kept. Brewster was working on his Memoirs of the life, writings, and discoveries of Sir Isaac Newton, (Edinburgh: Constable etc., 1855), supplementary to his Life of Newton (London: J. Murray, 1831). [See also Doc. No: 03498].