Warren De La Rue to Faraday   11 October 1856

London, 110 Bunhill Row. | October 11 1856

My dear Mr Faraday,

I returned only yesterday from Paris through which I passed on my way homeward from Caen in Normandy. I met Graham there and we called together on Pelouze¹ who informed us that Mitscherlich² was staying at the Hotel des Princes:- we called but he was unfortunately out. The Paris Mint is overwhelmed with gold which it fails to manufacture fast enough to supply the place of the place of the absent silver five-franc pieces, and much uneasiness exists in Paris as to the result of this monetary disturbance³. The processes of manufacture in the Paris mint appear to me to [be] very rough more especially in the founding and rolling of the metals as more than 20 po/o of “blanks” are rejected for errors of weight or defects, and upwards of 10 po/o of the coined pieces & I believe in the London Mint the total rejections do not exceed 5 p0/0 in both stages.

Gold leaf

The depolarizing effects which I noticed in gold leaf were obtained by putting the gold leaf on a copper frame with a long slit in it, and holding one or two of these inclined before a lighted taper at an angle of 45° & viewing the transmitted light through a Nichol’s prism which was revolved in the hand. I have not repeated the experiment but I will do so⁴.

Yours very truly | Warren De la Rue