TALBOT3506

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 M^r 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 exp^t 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 Exp^t. on the Iodide of Lead ⁶ is in the highest degree beautiful.– You do wrong in publishing so important an Exp^t among others. It should have formed a separate article in order to attract the attention wh^h 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 8^th May, and if you sh^d 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 29^th 1837