TALBOT3337

Edin^r 6 Dundas Street
July 16^th 1836

My Dear Sir,

I have only this moment received your letter of the 10^th July, ¹ in consequence of its being addressed to me at Belleville. ² It would have given me the highest pleasure to have accepted of your kind invitation ³ to Lacock Abbey had it been in my power to attend the meeting of the Association at Bristol; but I am at present endeavouring to make arrangements to go to the continent in consequence of the illness of Lady Brewster ⁴ to whom a temporary residence in a warmer climate has been recommended, and I have therefore found it impracticable to undertake so long a journey as that which the Association requires this year from its members. The vexation which this had occasioned me before the receipt of your letter has been greatly aggravated by the additional sacrifice which I make in declining your kind hospitality.

I received your account & sketches of the Circular crystals; ⁵ but being in a state of transition from a secluded to a wandering life I had not time to get the crystals made and examined. The subject is most curious & you should exhaust it before you allow it to go into other hands.

The structure of Tincal or Native Boron, and also of the Borax of the Shops is bi-axal. The last time I saw Sir John Herschel ⁶ at Slough he shewed me a very curious experiment with Borax which proved ocularly the truth discovered by Fresnel ⁷ that what is called the ordinary image is formed by the law of extraordinary refraction in bi-axal crystals. The experiment consisted in viewing thro' two inclined faces of the crystals a long line of light, such as the opening between partially closed window shutters.

The crystals which you mention as absorbing polarised light totally, tho' microscopic, are highly interesting. You ought to have accurate d[rawings]⁸ made of all the phenomena of coloured crosses formed by the circular crystals, otherwise those who follow you in the inquiry, & who do this, will receive all the credit due to you even tho' they represent nothing more than you have seen.

I am My Dear Sir Ever Most Faithfully yrs
D Brewster

H.F. Talbot Esq^r
Lacock Abbey
Chippenham