[Illustration] SCIENTIFIC AMERICAN SUPPLEMENT NO. 484 NEW YORK, APRIL 11, 1885 Scientific American Supplement. Vol. XIX, No. 484. Scientific American established 1845 Scientific American Supplement, $5 a year. Scientific American and Supplement, $7 a year. * * * * * TABLE OF CONTENTS. I. ENGINEERING AND MECHANICS.--Bridge over the Blaauw Krantz Ravine, Cape Colony.--2 engravings. Torpedo Ships. The Gas Engine.--By DUGALD CLERK.--Combustion engines.--First cylinder and piston engine.--Watt's experiments.--First gas engine.--Principles of the gas engine. Rapid Construction of the Canadian Pacific Railway.--By E.T. ABBOTT. The Osgood Mammoth Excavator.--3 figures. Capstan Navigation on the Volga.--4 figures. Steamboat Equipment of War Vessels.--With engraving of winch for raising and lowering torpedo boats. Improved Steam Trap.--1 engraving. II. TECHNOLOGY.--Critical Methods of Detecting Errors in Plane Surfaces.--By JOHN A. BRASHEAR.--11 figures. Photometric Standards.--9 figures. Bleaching or Dyeing Yarns and Goods in Vacuo.--1 figure. On the Moulding of Porcelain.--By CHAS. LAUTH.--Moulding by pressure of the air.--Moulding by vacuum.--Drying the moulded pieces.--2 figures. Photo-Tricycle Apparatus.--1 figure. A Photo Printing Light.--1 figure. A New Actinometer. Astronomical Photography. Electricity as a Preventive of Scale in Boilers. III. DECORATIVE ART.--Alphabet designed by Godfrey Sykes.--An engraving. Old Wrought Iron Gate.--An engraving. IV. GEOLOGY.--The Organization and Plan of the United States Geological Survey.--By J.W. POWELL.--A topographic map of the United States.--Paleontology.--Chemistry.--Physical researches.--Statistics.--Library.--Publications.--General geology.--Economic geology.--Relation of the general survey to the State survey. V. BOTANY, ETC.--The Sunflowers.--Annuals, perennials, etc.--11 engravings. Lye's Fuchsias.--1 engraving. VI. HYGIENE, ETC.--Brief Sanitary Matters in Connection with Isolated Country Houses.--By E.W. BOWDITCH. Sanitary Cooking.--By V.L. OPPENHEIMER. Time required to digest Different Foods. * * * * * THE BLAAUW KRANTZ VIADUCT IN CAPE COLONY.