the similarity in natives of the South American Andes.  Of a large collection made by Professor Royle, in the Himalayas, Don pronounced almost every one to be identical with European species.  From examining the raw vegetable products, sent by different countries to the Great Exhibition of 1851, I am satisfied that, even now, there are many fields open for the establishment of an export trade in Roccellas and other so-called orchella weeds.”  I there saw specimens of good dye lichens from almost every part of the world, including our own young colonies; and as a single instance of their probable value, I may introduce here the copy of a note appended to a specimen of orchella weed from the island of Socotra, contained in the Indian collection of that exhibition, “abundant, but unknown as an article of use or commerce.  Also abundant on the hills around (Aden) and might be made an article of trade.”  Roccellas from this source are estimated as worth L190 to L380 per ton.  I believe that a similar statement might be made with regard to the countless islands of the broad Atlantic and Pacific, which may, at some future period, perhaps not far distant, be found to be rich depots of orchella weeds, just as some of them are, at present, rich fields of guano, and may, as such, become new nuclei of British commerce and enterprise.  Even at home, in the immediate vicinity of Edinburgh, or, to restrict our limits still more narrowly, within the compass of Arthur’s Seat, there are not a few very good dye-lichens, which require merely to be scraped with an old knife or similar instrument, from the rocks to which they adhere, and subjected to the ammonia process already mentioned.  Of twelve specimens thus collected at random one morning, I found no less than three yielded beautiful purple-red colors, apparently as fine as orchil or cudbear, while the others furnished rich and dark tints of brownish-red, brown and olive-green.

    Dr. Lindley’s communication was illustrated with specimens of
    coloring matters yielded by various lichens collected in the
    neighbourhood of Edinburgh, &c.

BARKS FOR TANNING.

Let us now take a brief review of the sources from whence tanning materials may be obtained, which will also enable us to form a fair estimate of the prospect of future supplies.  Only one medal was awarded, at the Great Exhibition, for tanning substances, viz., to Messrs. Curtis, Brothers (United Kingdom, No. 126), but honorable mention was made of the following competitors:—­One from Tunis, one from Van Diemen’s Land, one from New Zealand, one from Belgium, one from the Cape of Good Hope, one from Canada, and one from the United Kingdom.

The substance from which pure tannin is most frequently obtained for chemical purposes is nutgalls, for tannin constitutes above 40 per cent, of their weight.  It may be procured also from several other sources, such as oak, horse chestnut, sumach, and cinchona barks, catechu, kino, &c.