Page:Philosophical Transactions - Volume 104.djvu/483

41 8 Dr. Brewster on new Properties of light, &c. 1. That mother of pearl polarises light in a manner different from all crystallised bodies, the polarisation having no reference to any fixed line in the plate.

2. That mother of pearl polarises light in a manner different from all uncrystallised bodies, the transmitted pencil being wholly polarised by a single plate, and in the same manner with the reflected pencil.

3. That if mother of pearl polarises light in virtue of its laminated structure, the laminæ themselves must have the property of polarising light in a manner opposite to all other bodies.

I have thus endeavoured to explain, as briefly as possible, the various phenomena exhibited by mother of pearl in its action upon light. The subject, however, is far from being exhausted: it still presents many points of interesting inquiry; and if the investigation could be carried on with the aid of analogous phenomena, we might confidently look forward to some great change in the fundamental principles of physical optics.

I have the honour to be, Sir, your most obedient and humble servant, DAVID BREWSTER.

Edinburgh, February 28th, 1814.

To the Right Hon. Sir, Bart. K. B. P. R. S. &c. &c. &c.