A Practical Engineer and Machinist, 24 years' experience. Best of reference, marine or stationary; forge; fit; repair. W. Barker, 433 2d Ave., N. Y. Hydraulic Presses and Jacks, new and second hand. Lathes and Machinery for Polishing and Buffing metals. E. Lyon & Co., 470 Grand St., N. Y. Nickel Plating.--A white deposit guaranteed by using our material. Condit, Hanson & Van Winkle, Newark, N. J. Cheap but Good. The "Roberts Engine," see cut in this paper, June 1st, 1878. Also horizontal and vertical engines and boilers. E. E. Roberts, 107 Liberty St., N. Y. The Cameron Steam Pump mounted in Phosphor Bronze is an indestructible machine. See ad. back page. Presses, Dies, and Tools for working Sheet Metals, etc. Fruit and other Can Tools. Bliss & Williams, Brooklyn, N. Y., and Paris Exposition, 1878. The SCIENTIFIC AMERICAN Export Edition is published monthly, about the 15th of each month. Every number comprises most of the plates of the four preceding weekly numbers of the SCIENTIFIC AMERICAN, with other appropriate contents, business announcements, etc. It forms a large and splendid periodical of nearly one hundred quarto pages, each number illustrated with about one hundred engravings. It is a complete record of American progress in the arts. Bound Volumes of the Scientific American.--I will sell bound volumes 4, 10, 11, 12, 13, 16, 28, and 32, New Series, for $1 each, to be sent by express. Address John Edwards, P. O. Box 773, New York. For Solid Wrought Iron Beams, etc., see advertisement. Address Union Iron Mills, Pittsburgh, Pa., for lithograph, etc. Pulverizing Mills for all hard substance and grinding purposes. Walker Bros. & Co., 23d and Wood St., Phila. 2d hand Planers, 7' x 30", $300; 6' x 24", $225; 5' x 24", $200; sc. cutt. b'k g'd Lathe, 9' x 28", $200; A. C. Stebbins, Worcester, Mass. J. C. Hoadley, Consulting Engineer and Mechanical and Scientific Expert, Lawrence, Mass. Best Wood Cutting Machinery, of the latest improved kinds, eminently superior, manufactured by Bentel, Margedant & Co., Hamilton, Ohio, at lowest prices. Water Wheels, increased power. O. J. Bollinger, York, Pa. We make steel castings from ¼ to 10,000 lbs. weight. 3 times as strong as cast iron. 12,000 Crank Shafts of this steel now running and proved superior to wrought iron. Circulars and price list free. Address Chester Steel Castings Co., Evelina St., Philadelphia, Pa. Diamond Saws. J. Dickinson, 64 Nassau St., N. Y. Machine Cut Brass Gear Wheels for Models, etc. (new list). Models, experimental work, and machine work generally. D. Gilbert & Son, 212 Chester St., Phila., Pa. Holly System of Water Supply and Fire Protection for Cities and Villages. See advertisement in Scientific American of last week.