Warren De La Rue to Faraday   13 October 1856

London, 110 Bunhill Row. | October 13 1856

My dear Mr Faraday

I have repeated the experiment with the gold leaf:-

I find that light passing through a gold leaf held at an angle say of 45° is polarized, and hence that an obscuration and lightening are produced alternately if the light is viewed through a Nicholl’s prism made to rotate.

If the light is first polarized and the analyzer arranged to produce obscuration then the interposition of the gold leaf renders the flaw visible, as you state in your note.

I believe that your explanation is the true one for both cases, and hence that there is no polarization produced by the gold leaf in consequence of the compression by hammering¹.

Yours Very truly | Warren De la Rue