THE COPYING PAD.--HOW TO MAKE and how to use; with an engraving. Practical directions how to prepare the gelatine pad, and also the aniline ink by which the copies are made; how to apply the written letter to the pad; how to take off copies of the letter. Contained in SCIENTIFIC AMERICAN SUPPLEMENT, No. =438.= Price 10 cents. For sale at this office and by all newsdealers in all parts of the country. [Illustration] Syracuse Malleable Iron Works THE ERODING POWER OF ICE.--A paper by Dr. J. S. Newberry, discussing the reality of a glacial period, and the importance of glaciers as geological agents. Glacial Topography, Drift Deposits. Excavation of Lake Basins, Mode of Glacial Erosion. Contained in SCIENTIFIC AMERICAN SUPPLEMENT, No. =499.= Price 10 cents. To be had at this office and from all newsdealers. 2d HAND MACHINERY Lists sent. N.Y. Machinery Depot, Bridge Store No. 16, Frankfort Street, N.Y. INGERSOLL ROCK DRILL CO., 10 PARK PLACE, NEW YORK. Improved "Eclipse" ROCK DRILLS. For Mining, Tunneling, Shaft-Sinking, Quarrying, Submarine drilling, and for all kinds of rock excavation. "Straight Line" AIR COMPRESSORS, Boilers, Steam and Horse Power Hoists, Electric Blasting Batteries and General Mining Machinery. Send for full descriptive Catalogue. The New Catalogue of Valuable Papers contained in SCIENTIFIC AMERICAN SUPPLEMENT, sent _free of charge_ to any address. MUNN & CO., 361 Broadway, N Y Edco System =Of Arc and Incandescent Lighting. Electric Light and Power.= Motors, Dynamos, Lamps, and Batteries in all varieties. Electro-Dynamic Co., 224 Carter St., Philadelphia. =W. W. Griscom, Consulting Electrical Engineer= A FEW CHOICE TECHNICAL BOOKS. RECENTLY PUBLISHED. =Crew.=--A Practical Treatise on Petroleum. Comprising its Origin, Geology, Geographical Distribution, History, Chemistry, Mining, Technology, Uses and Transportation. Together with a description of Gas Wells, the application of Gas as Fuel, etc. By BENJAMIN J. CREW. With an Appendix on the Product and Exhaustion of the Oil Regions, and the Geology of Natural Gas in Pennsylvania and New York. By CHARLES A. ASHBURNER, M.S., Geologist in Charge Pennsylvania Survey, Philadelphia. Illustrated by 70 engravings. 8vo. 508 pages, $4.50 =Richards.=--Aluminium: Its History, Occurrence, Properties, Metallurgy and Applications, including its Alloys. By JOSEPH W. RICHARDS, A.C., Chemist and Practical Metallurgist, Member of the Deutsche Chemische Gesellschaft. Illustrated by 16 engravings. 12mo. 346 pages, $2.50