[Illustration] SCIENTIFIC AMERICAN SUPPLEMENT NO. 483 NEW YORK, APRIL 4, 1885 Scientific American Supplement. Vol. XIX, No. 483. Scientific American established 1845 Scientific American Supplement, $5 a year. Scientific American and Supplement, $7 a year. * * * * * TABLE OF CONTENTS. I. CHEMISTRY AND METALLURGY.--The Determination of Graphite in Minerals.--By J.B. MACKINTOSH. Sulphocyanide of Potassium. Sugar Nitro-glycerine. On Remelting of Cast Iron. The Hardness of Metals. II. ENGINEERING, ETC.--The Jet Ventilator. 4 figures. Feeding Boilers at the Bottom. 2 figures. The Honigmann Fireless Engine.--The fireless working of steam engines by means of a solution of hydrate of soda.--With several figures and diagrams. Simple Methods of Calculating Stress in Girders.--By CH. LEAN.--With full page of illustrations. A Spring Motor. Steam Yachts. III. TECHNOLOGY.--Foucault's Apparatus for Manufacturing Illuminating Gas and Hydrogen. 2 figures. The Circle Divider. Soluble Glass.--Process of manufacture.--Use. Iron Printing and Microscopic Photography.--Formulas for printing solutions.--Compound negatives. Practical Directions for Making Lantern Transparencies.--By T.N. ARMSTRONG. Casting Chilled Car Wheels. 6 figures. IV. ELECTRICITY, ETC.--Electricity and Prestidigitation. 2 figures. Portable Electric Safety Lamp. 6 figures. The Electric Discharge and Spark Photographed Directly without an Objective. 6 engravings. V. PHYSICS, ETC.--The True Constant of Gravity. Origin of Thunder Storms. Physics without Apparatus.--Manufacture of illuminating gas.--Elasticity of bodies. 2 figures. Scientific Amusements.--Dance of electrified puppets.--Silhouette portraits. 2 figures. A Sunshine Recorder. 2 figures. VI. MEDICINE, HYGIENE, ETC.--How Cholera is Spread. Sulphurous Acid and Sulphide of Carbon as Disinfecting Agents.--Methods of burning the same. VII. MISCELLANEOUS.--Improvised Toys.--With numerous illustrations. The Æolian Harp.--Kircher's harp, made in 1558.--Frost and Kastner's harp.--Manner of making the harps. 4 figures. How to Break a Cord with the Hands. 1 figure. An Aquatic Velocipede for Duck Hunting. 2 engravings. Skeleton of a Bear Found in a Cave in Styria, Austria. VIII. BIOGRAPHY.--Theodor Billroth, Prof, of Surgery at Vienna.--With portrait. * * * * * ACKNOWLEDGMENT. The illustrations and descriptions we give this week, entitled "How to Break a Cord," "Prestidigitation," "Circle Divider," "Sulphurous Acid," "Production of Gas," "Aquatic Velocipede," "Several Toys," "Scientific Amusements," are from our excellent contemporary _La Nature_. * * * * *