Produced by Olaf Voss, Don Kretz, Juliet Sutherland, Charles Franks and the Online Distributed Proofreading Team. [Illustration] SCIENTIFIC AMERICAN SUPPLEMENT NO. 303 NEW YORK, OCTOBER 22, 1881 Scientific American Supplement. Vol. XII, No. 303. Scientific American established 1845 Scientific American Supplement, $5 a year. Scientific American and Supplement, $7 a year. * * * * * TABLE OF CONTENTS I. ENGINEERING AND MECHANICS.--New Eighty-ton Steam Hammer at the Saint Chamond Works, France.--7 figures.--Elevation of hammer.--Profile-- Transverse section.--Profile view of foundation, etc.--Plan of plant.--General plan of the forging mill.--Details of truss and support for the cranes. Great Steamers.--Comparative details of the Servia, the City of Rome, the Alaska, and the Great Eastern. Improved Road Locomotive.--2 figures.--Side and end views American Milling Methods. By ALBERT HOPPIN.--Ten years' progress.--Low milling.--Half high milling.--High milling.--Important paper read before the Pennsylvania State Millers' Association. Machine for Dotting Tulles and other Light Fabrics.--3 figures. II. TECHNOLOGY AND CHEMISTRY.--The Reproduction and Multiplication of Negatives. By ERNEST EDWARDS. A New Method of Making Gelatine Emulsion. By W. K. BURTON. The Pottery and Porcelain Industries of Japan. Crystallization Table. The Principles of Hop Analysis. By Dr. G. O. CECH. Water Gas.--A description of apparatus for producing cheap gas, and some notes on the economical effects of using such gas with gas motors, etc.--By J. EMERSON DOWSON. On the Fluid Density of Certain Metals. By Professors CHANDLER ROBERTS and T. WRIGLESON. III. PHYSICS, ELECTRICITY, ETC.--Electric Power.--The nature and uses of electricity.--Electricity vs. steam. On the Method of Obtaining and Measuring Very High Vacua with a Modified Form of Sprengel Pump. By Prof OGDEN N. ROOD.--4 figures.-- Apparatus for obtaining vacua of one four hundred-millionth of an atmosphere--Construction.--Manipulation.--Calculations.--Results IV. ART, ARCHITECTURE, ETC.--Old Wrought Iron Gates, Guildhall. Worcester, England. 1 figure. The French Crystal Palace, Park of St. Cloud, Paris. 1 full page illustration. Suggestions in Architecture. A Castellated Chateau. Perspective and plan. Chateau in the Ægean Sea. V. HYGIENE AND MEDICINE.--Hydrophobia Prevented by Vaccination. On Diptera as Spreaders of Disease. By J. W. SLATER. On the Relations of Minute Organisms to Certain Specific Diseases. VI. ASTRONOMY--The Centenary of the Discovery of Uranus. By F. W. DENNING. 2 figures. Approximate place of Uranus among the stars at its discovery, March l3, 1871.--Orbits of the Uranian Satellites.