Nowhere is this more urgently needed than in the whole field of glass manufacture. The author is indebted to Mr. W. C. Hancock for valuable assistance in the reading of proofs and various suggestions in connection with the contents of this book. TABLE OF CONTENTS PAGE PREFACE v CHAPTER I. THE PHYSICAL AND CHEMICAL PROPERTIES OF GLASS. Definition of the term “Glass”--Amorphous structure the common feature of all vitreous bodies--Glass a congealed fluid--Glasses not definite chemical compounds but complex solutions--Range of chemical composition available for glass-making--Considerations governing chemical composition--Influence of composition on physical properties--Chemical stability of glass-- Permanence of glass surfaces--Action of water, acids, and alkalies on glass--Action of light on glass _p._ 1 CHAPTER II. THE PHYSICAL PROPERTIES OF GLASS. Mechanical properties: tensile strength, crushing strength, elasticity, ductility, and hardness--Thermal properties of glass: thermal endurance, coefficient of expansion, thermal conductivity--Thermometer glass--Electrical properties of glass--Transparency and colour of glass _p._ 18 CHAPTER III. THE RAW MATERIALS OF GLASS MANUFACTURE. General considerations--Chemical purity, moisture, and physical condition, constancy of quality--Sources of silica, sand and sandstone--Felspar--Sources of alkali: Soda ash (carbonate of soda), salt-cake (sulphate of soda), pearl ash (carbonate of potash)--Alkali nitrates--Natural minerals containing alkalies--Sources of other bases: Lime, chalk, limestone, slaked lime-- Gypsum (sulphate of lime)--Barium compounds--Magnesia and zinc--Lead oxide, red lead--Aluminium, manganese, arsenic--Carbon--Coke, charcoal, anthracite coal _p._ 35 CHAPTER IV. CRUCIBLES AND FURNACES FOR THE FUSION OF GLASS. Fire-clay and silica-brick--Manufacture of glass-melting pots--Drying and first heating of pots--Blocks for tank and other furnaces--Uses of silica brick--Furnaces-- Coal-fired and gas-fired furnaces--Gas producers-- Regenerative furnaces, principles and construction of Siemens’ furnaces--Recuperative furnaces--General arrangements of modern tank furnaces--Relative advantages of tank and pot furnaces _p._ 54 CHAPTER V. THE PROCESS OF FUSION. Mixing of raw materials by hand and by machinery--The charging operation--Chemical reactions during melting of carbonate mixtures, and of sulphate mixtures--Influence of carbon on the reactions--The fining process _p._ 73 CHAPTER VI. PROCESSES USED IN THE WORKING OF GLASS.