Method of feeding it 257 Combustion of Gas in Flues 260 Williams's Patent for Method of consuming unburned Gases 260 Construction of Grate and Ash-pit 261 Magnitude of heating Surface of Boiler 262 Steam-space and Water-space in Boiler 263 Position of Flues 264 Method of feeding Boiler 265 Method of indicating the Level of Water in Boiler 266 Level Gauges 266 Self-regulating Feeders 267 Steam Gauge 270 Barometer Gauge 272 Watt's Invention of the Indicator 274 Counter 278 Safety-valve 279 Fusible Plugs 280 Self-regulating Damper 281 Brunton's Self-regulating Furnace 283 Gross and useful Effect of an Engine 285 Power and Duty of Engines 287 Horse-power of Steam Engines 289 Evaporation proportional to Horse-power 290 Sources of Loss of Power 292 Absence of good practical Rules for Power 292 Common Rules followed by Engine-makers 292 Duty distinguished from Power 294 Duty of Boilers 294 Proportion of Stroke to Diameter of Cylinder 295 Duty of Engines 296 Cornish System of Inspection 297 Table showing the Improvement of Cornish Engines 298 Beneficial Effects of Cornish Inspection 299 Successive Improvements on which the increased Duty of Engines depends, traced by John Taylor in his "Records of Mining" 299 CHAP. X. LIFE OF WATT. Watt's Friends and Associates at Birmingham 302 His Invention of the Copying Press 302 Heating Apartments and Buildings by Steam 303 Watt's Machine for drying Linen 303 His Share in the Discovery of the Composition of Water 303 The Merit of this Discovery shared between Cavendish, Lavoisier, and Watt 305 Anecdote of Watt's Activity of Mind 309 His Introduction of the Use of Chlorine in Bleaching 310 One of the Founders of the Pneumatic Institution at Clifton 310 His first Marriage 311 Death of his first Wife 311 His second Marriage 311