[Illustration] SCIENTIFIC AMERICAN SUPPLEMENT NO. 520 NEW YORK, DECEMBER 19, 1885 Scientific American Supplement. Vol. Vol. XX, No. 520. Scientific American established 1845 Scientific American Supplement, $5 a year. Scientific American and Supplement, $7 a year. * * * * * TABLE OF CONTENTS. I. ENGINEERING, ETC.--Steel Structures.--Best use of different grades of steel.--From a paper by Mr. JAS. CHRISTIE. Natural Gas Fuel and its Application to Manufacturing: Purposes.--Paper read before the Iron and Steel Institute by Mr. ANDREW CARNEGIE.--First use of the gas.--Wells near Pittsburg.--Extent of territory underlain with gas.--Cost of piping.--Analyses ofnatural gas. A Gas Engine Water Supply Alarm.--1 figure. The Water Supply of Ancient Roman Cities.--An address by Prof. W.H. CORFIELD.--Aqueducts for the supply of Borne.--The aqueduct bridge Pont du Gard.--The supply of Lyons.--Construction of underground aqueducts. Steam Engine Economy.--By Chief Engineer J. LOWE, U.S.N.--With diagram. The "Elastic Limit" in Metals.--Selection of wire for suspension bridges, etc. Prices of Metals in 1874 and 1884.--With table. II. TECHNOLOGY.--A Method of Measuring the Absolute Sensitiveness of Photographic Dry Plates.--By Wm. H. PICKERING.--From the proceedings of the Academy of Arts and Sciences. Soldering and Repairing Platinum Vessels in the Laboratory.--By J.W. PRATT. The Helicoidal or Wire Stone Saw invented by M.P. GAY.--With engraving of quarry showing application of saw, and 5 figures. Portable Prospecting Drill and Automatic Safety Gear shown at the Inventions Exhibition.--With 2 engravings. III. ELECTRICITY, ETC.--Electricity in Warfare.--By Lieutenant B.A. FISKE, U.S.N.--Electrical torpedoes.--Torpedo detecter.--Military telegraphy and telephony.--Electricity for firing great guns.--Arrangement of wires for lights.--The search light.--Incandescent lamps for sight signaling.--Electrical launches.--An "electric sight". Meucci's Claims to the Telephone.--With description of his instrument and 10 figures. An Electric Centrifugal Machine for Laboratories.--By ALEX. WATT.--From paper read before the British Association.--1 figure. Transmission of Power by Electricity.--Experiments of M. MARCEL DEPREZ. IV. ART AND ARCHITECTURE.--Quadriga for the New House of Parliament at Vienna.--An engraving. Glazed Ware Finial.--With engraving. Hotel de Ville, St. Quentin.--With engraving. Fire Doors in Mills.--From a lecture before the Franklin Institute by C.J. HEXAMER. V. NATURAL HISTORY, ETC.--Preservation of Insects. An Accomplished Parrot.