On the wall against which this monument is built, feathers are sculptured, forming a canopy. Such a superb _chef d'oeuvre_ proves beyond doubt that the Maya artists were in no way inferior to those of Assyria and Egypt. Having been so unjustly deprived of Chaacmol without any remuneration for our time, labor, and expenditure, we decided to save the Cay monument from destruction at any cost, for should any ignorant persons attempt to move it, they would break it in so doing; so, after making a mould of it, we guarded it most securely, as we considered best, afterward inclosing it with planks, then built it up and left it as we had found it. Sr. Don Romero Ancona, then Governor of Yucatan, was very much provoked because we would not reveal the whereabouts of our find, but gained nothing by it, and the beautiful monument is still safe. ALICE D. LE PLONGEON. * * * * * Rolled gold is made by casting an ingot of brass, and while this is still hot pouring upon it a thin layer of gold alloy. The ingot when cold is forced between steel rollers until a long, thin ribbon is produced, of which the proportion of gold and brass is the same as of the ingot. The percentage of gold is reduced as low as two and three per cent. This rolled gold is used in making cheap bracelets and watch chains. It wears from one to ten years. A CATALOGUE, containing brief notices of many important scientific papers heretofore published in the SUPPLEMENT, may be had gratis at this office. * * * * * The Scientific American Supplement. PUBLISHED WEEKLY. TERMS OF SUBSCRIPTION, $5 A YEAR. Sent by mail, postage prepaid, to subscribers in any part of the United States or Canada. Six dollars a year, sent, prepaid, to any foreign country. All the back numbers of THE SUPPLEMENT, from the commencement, January 1, 1876, can be had. Price, 10 cents each. All the back volumes of THE SUPPLEMENT can likewise be supplied. Two volumes are issued yearly. Price of each volume, $2.50, stitched in paper, or $3.50, bound in stiff covers. COMBINED RATES--One copy of SCIENTIFIC AMERICAN and one copy of SCIENTIFIC AMERICAN SUPPLEMENT, one year, postpaid, $7.00. A liberal discount to booksellers, news agents, and canvassers. MUNN & CO., PUBLISHERS, 261 BROADWAY, NEW YORK, N.Y. * * * * * PATENTS. In connection with the SCIENTIFIC AMERICAN, Messrs. MUNN & Co. are Solicitors of American and Foreign Patents, have had 38 years' experience, and now have the largest establishment in the world. Patents are obtained on the best terms. A special notice is made in the SCIENTIFIC AMERICAN of all Inventions patented through this Agency, with the name and residence of the Patentee. By the immense circulation thus given, public attention is directed to the merits of the new patent, and sales or introduction often easily effected.