General Principles—Practical Forms of Radiation Pyrometers—Féry’s Mirror Pyrometer—Féry’s Spiral Radiation Pyrometer—Foster’s Fixed-Focus Radiation Pyrometer—Paul’s Radiation Pyrometer—Indicators for Radiation Pyrometers—Calibration of Indicators— Recorders—Management of Radiation Pyrometers—Special Uses of Radiation Pyrometers. VI. OPTICAL PYROMETERS 167 General Principles—Wien’s Law—Practical Forms of Optical Pyrometers—Féry’s Optical Pyrometer—Le Chatelier’s Optical Pyrometer—Wanner’s Pyrometer— Cambridge Optical Pyrometer—Holborn-Kurlbaum Pyrometer—Lovibond’s Pyrometer—Mesuré and Nouel’s Pyrometer—Colour-extinction Pyrometers— Management of Optical Pyrometers—Special Uses of Optical Pyrometers. VII. CALORIMETRIC PYROMETERS 195 General Principles—Practical Forms—Siemens’ Calorimetric or “Water” Pyrometer—Special Uses. VIII. FUSION PYROMETERS 204 General Principles—Seger Pyramids or “Cones”— Watkin’s Heat Recorder—“Sentinel” Pyrometers— Stone’s Pyrometer—Fusible Metals—Fusible Pastes. IX. MISCELLANEOUS APPLIANCES 211 Expansion and Contraction Pyrometers—Wedgwood’s Pyrometer—Daniell’s Pyrometer—Northrup’s Molten Tin Pyrometer—Vapour-Pressure Pyrometers—Water-Jet Pyrometers—Pneumatic Pyrometers—Conduction Pyrometers—Gas Pyrometers—Wiborgh’s Thermophones— Joly’s Meldometer—Brearley’s Curve Tracer. INDEX 222 Preface to the Second Edition Since the publication of the first edition in 1911, a great extension has been witnessed in the use of pyrometers in industrial processes and laboratory work, to which development the author hopes his book has contributed in some measure. During the stress occasioned by the war, pyrometers have proved invaluable in many processes, and British makers were fully able to meet the demands, owing to the status attained in pre-war days. The increasing use of pyrometric appliances renders necessary some book of reference which will provide the user with information to enable him to get the best results out of his instruments, and it is hoped that the present treatise meets this need. In preparing the second edition, certain parts have been revised in conformity with modern practice, and the later developments included. The scope of the book remains as before. The author desires to acknowledge the assistance he has received from the British makers of pyrometers, all of whom have liberally provided him with information of a most useful kind, of which he has availed himself in the production of the present edition.