In adding aluminum to the copper, cut it in small pieces and push it to the bottom of the crucible with a dry, hard wood stick split so as to hold the pieces. Sodium chloride (common salt) calcined to evaporate the water, and caustic soda with pulverized charcoal, may be used as a flux for pure aluminum. Avoid borax as a flux, as its metal may suffer reduction, making the aluminum brittle. Aluminum will alloy with tin alone, but is liable to separate on refusion. Does not alloy with lead. Bismuth, even in minute quantity, makes these alloys brittle. The East Indian steel called _wootz_ is, according to analysis, alloyed with aluminum. No reliable solder has yet been found for pure aluminum that will flow freely under the blow pipe or from a soldering iron. A process recently adopted in France is to plate the parts to be united with alloys of tin 5, aluminum 1, upon which tin solder will flow. These proportions may be slightly varied to suit requirements for hardness. Harder solders to be used with a blowpipe may be made with alloys of zinc, tin, and aluminum. Aluminum is now made at the works of M. Deville, at Javelle, near Paris, and at Salindres, France; also at Birmingham, England. The product of late has reached the value of $20,000 annually in Europe. It has been claimed to be made in Philadelphia at a reduced cost. The present price in New York is $1.25 per oz. As its bulk is over four times as great as silver, its comparative cost is but one-third that of silver--a point not often considered when the price is quoted. * * * * * 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,+ 361 Broadway, New York, N. Y. * * * * * TABLE OF CONTENTS. PAGE I. CHEMISTRY AND METALLURGY.--Determination of Tannin.--By E. JOHANSON. 7458