TALBOT4190

Dear Sir,

I return your two Portraits ¹ with many thanks. After exhibiting them at my Lecture which was well received, I sent them to Lord Gray ² who was very anxious to see them; but having laid them up too carefully I did not receive them from his Lordship till this morning. ³

I am glad you have taken out a Patent. To extend it to Scotland w^d be unprofitable. ⁴ I am very anxious to hear the particulars of your new Process ⁵ and to see its effects.

I have succeeded in obtaining some very important results respecting the polarising structure of the Atmosphere;– the Compensation of polarised light, and the phenomena of thin Plates seen by polarised light, which will form three Papers ⁶ for the Royal Society.

The results regarding the Atmosphere are very singular. Arago ⁷ & Babinet ⁸ each discovered a Neutral point. There are 4 neutral points ⁹ produced by the opposite actions of Reflexion & Refraction, which are the cause of all the phenomena of atmospheric Polarisation. The Reflective influence predominates in a clear sky; but in cloudy or hazy weather it is often destroyed by the Refractive influence which sometimes predominates over it.

I am Dear Sir Ever Most Truly yrs
D Brewster

S^t Leonards
St Andrews
Feb^y 4^th 1841

H.F. Talbot Esq^r