Marine Iron Works. Chicago. Catalogue free. C. S. metal polish. Indianapolis. Samples free. Presses & Dies. Ferracute Mach. Co., Bridgeton, N. J. Handle & Spoke Mcby. Ober Latbe Co,,Cbagrin Falls.O. For mud dredging engines. J. S Mundy, Newark, N. J. Inventive problems and ideas worked out. See advt, page 367. Screw macbines, milling macmnes, and drill presses. The Garvin Mach. Co . , Laieht and Canal Sts.. New York. Emerson, Smith & Co., Ltd., Beaver Falls, Pa. , will send Sawyers Hand Book on Circulars and Band Saws free to any address . Practical Electrics.—Tbe most complete book on electrical matters, fully illustrated. 8vo, clotb, 75 cents. Spon & Cbamberlain, 12 Cortlandt St., New York. The best book for electricians ana beginners in electricity is Experimental Sclence;by Geo. Hopkins. By mail. $4 ; Munn & Co., publishers, 361 Broadway, N. Y For the original Bogardus Universal Eccentric Mill, Foot and Power Presses, Drills, Shears, etc., address J.S. & G. F. Simpson, 26to 36 Rodney St., Brooklyn, N. Y. p-ilend for new and complete catalogue of Scientific and other Books for sale by Munn & Co. . 361 Broadway, New York. Free on application.