Vienna, 14 Nov. 1852.

Dear Sir,

I beg leave to introduce myself, and to address you directly. I have read a notice on the interesting crystals with a, metallic surface, you described at the Belfast meeting. I enclose a small portion of crystals I examined some years ago, which I trust will be very interesting to you, as they almost exactly agree with those you examined, except in the point of transparency. The crystals I send are also allied to chinine. They were discovered by Prof. Wöhler, and named Grünes Hydrochinon. To him I have been indebted also for the small portion wrapt up here. The present crystals have evidently the same metallic aspect as those which you described, but they have a deep and beautiful violet blue colour by transmitted light. They are, however, but very faintly translucent, and in no direction they appear colourless or transparent, as it is said in the notice contained in Abbé Moigno's Cosmos 24 Octobre 1852, page 574.—There is also a mode of chemical preparation given there, but I failed in succeeding. Then I believe I can do nothing better, than asking you the favour yourself, in exchange for the small portion of hydrochinon, to send me also a very little quantity of the crystals you examined. Beside the one here included, I have examined a number of other crystals and substances shewing similar phenomena, and I lately drew up a catalogue of them, and presented it to our Academy. I sent a separate copy, inscribed to you, together with a number of others, to our mutual friend, Professor Miller, begging him to forward them to you.