[Illustration] SCIENTIFIC AMERICAN SUPPLEMENT NO. 787 NEW YORK, January 31, 1891 Scientific American Supplement. Vol. XXXI., No. 787. Scientific American established 1845 Scientific American Supplement, $5 a year. Scientific American and Supplement, $7 a year. * * * * * TABLE OF CONTENTS. I. BIOGRAPHY.--CHARLES GOODYEAR.--The life and discoveries of the inventor of vulcanized India rubber, with portrait.--1 illustration II. BIOLOGY.--Can we Separate Animals from Plants?--By ANDREW WILSON.--A debated point well discussed.--The bases on which distinctions must be drawn III. ELECTRICITY.--A New Electric Ballistic Target.--A target for investigations of the velocity of projectiles, now in use at the United States Military Academy, West Point, N.Y.--1 illustration. Electric Erygmascope.--An electric lighting apparatus for examining earth strata in bore holes for geologists' and prospectors' use.--1 illustration The Electro-Magnet.--By Prof. SILVANUS THOMPSON.--Continuation of this exhaustive treatise, giving further details on special points of construction.--1 illustrations IV. ENTOMOLOGY.--Potash Salts.--The use of potash salts as insecticides, with accounts of experiments The Outlook for Applied Entomology.--By Dr. C.V. RILEY, U.S. entomologist.--The conclusion of Prof. Riley's lecture, treating of the branch of entomology with which his name is so honorably associated V. INSURANCE.--The Expense Margin in Life Insurance.--Elaborate review of the necessary expenses of conducting the insurance of lives, with tables and calculations VI. MATHEMATICS.--The Trisection of Any Angle.--By FREDERIC R. HONEY, Ph.B.--A very ingenious demonstration of this problem, based on the properties of conjugate hyperbolas VII. METEOROLOGY.--Note on the Mt. Blanc Meteorological Station The Flood at Karlsbad.--Account of the recent flood and of its destructive effects.--1 illustration VIII. MECHANICAL ENGINEERING.--Station for Testing Agricultural Machines.--A proposed establishment for applying dynamometer tests to agricultural machines.--1 illustration Steam Engine Valves.--By THOMAS HAWLEY.--A review of modern slide valve practice, the lap, cut-off, and other points.--6 illustrations IX. MISCELLANEOUS.--Science in the Theater.--Curious examples of stage effect in fictitious mesmerizing and hypnotizing.--4 illustrations Theatrical Water Plays.--Recent episodes in real water plays at Hengler's Circus, London.--2 illustrations X. NAVAL ENGINEERING.--The French Ironclad War Ship Colbert.--An armored wood and iron ship, with central battery.--1 illustration