Produced by Chris Curnow, Paul Marshall and the Online Distributed Proofreading Team at http://www.pgdp.net (This file was produced from images generously made available by The Internet Archive Transcriber’s Notes: Underscores “_” before and after a word or phrase indicate _italics_ in the original text. Carat symbol “^” designates a superscript. A single underscore between two characters indicates a subscript. Equal signs “=” before and after a word or phrase indicate =bold= in the original text. Small capitals have been converted to SOLID capitals. Illustrations have been moved so they do not break up paragraphs. Typographical errors have been silently corrected but other variations in spelling and punctuation remain unaltered. PYROMETRY _BY THE SAME AUTHOR_ HEAT FOR ENGINEERS A TREATISE ON HEAT WITH SPECIAL REGARD TO ITS PRACTICAL APPLICATIONS Third Edition, revised, with 110 illustrations, xiv + 430 pp. Demy 8vo. Price 12s. 6d. net. LIQUID DROPS AND GLOBULES THEIR FORMATION AND MOVEMENT THREE LECTURES DELIVERED TO POPULAR AUDIENCES With 43 illustrations, x + 84 pp. Crown 8vo, cloth. Price 3s. net. E. & F. N. SPON, LTD., HAYMARKET, LONDON, S.W. 1 PYROMETRY A PRACTICAL TREATISE ON THE MEASUREMENT OF HIGH TEMPERATURES BY CHAS. R. DARLING ASSOCIATE OF THE ROYAL COLLEGE OF SCIENCE, DUBLIN; WHITWORTH EXHIBITIONER; FELLOW OF THE INSTITUTE OF CHEMISTRY; FELLOW OF THE PHYSICAL SOCIETY, ETC. LECTURER IN PHYSICS AT THE CITY AND GUILDS TECHNICAL COLLEGE, FINSBURY, E.C. AUTHOR OF “HEAT FOR ENGINEERS” SECOND EDITION, REVISED AND ENLARGED SIXTY-NINE ILLUSTRATIONS [Illustration] _London_ E. & F. N. SPON, Ltd., 57 HAYMARKET, S.W. 1 _New York_ SPON & CHAMBERLAIN, 120 LIBERTY STREET 1920 Contents PAGE PREFACE TO SECOND EDITION ix PREFACE TO FIRST EDITION xi CHAP. I. INTRODUCTION 1 II. STANDARDS OF TEMPERATURE 9