CONTENTS. Chapter I.--THE STEAM-ENGINE. What is steam?--The mechanical energy of steam--The boiler--The circulation of water in a boiler--The enclosed furnace--The multitubular boiler--Fire-tube boilers--Other types of boilers--Aids to combustion--Boiler fittings--The safety-valve--The water-gauge--The steam-gauge--The water supply to a boiler 13 Chapter II.--THE CONVERSION OF HEAT ENERGY INTO MECHANICAL MOTION. Reciprocating engines--Double-cylinder engines--The function of the fly-wheel--The cylinder--The slide-valve--The eccentric--"Lap" of the valve: expansion of steam--How the cut-off is managed--Limit of expansive working--Compound engines--Arrangement of expansion engines--Compound locomotives--Reversing gears--"Linking-up"--Piston-valves--Speed governors--Marine-speed governors--The condenser 44 Chapter III.--THE STEAM TURBINE. How a turbine works--The De Laval turbine--The Parsons turbine--Description of the Parsons turbine--The expansive action of steam in a Parsons turbine--Balancing the thrust--Advantages of the marine turbine 74 Chapter IV.--THE INTERNAL-COMBUSTION ENGINE. The meaning of the term--Action of the internal-combustion engine--The motor car--The starting-handle--The engine--The carburetter--Ignition of the charge--Advancing the spark--Governing the engine--The clutch--The gear-box--The compensating gear--The silencer--The brakes--Speed of cars 87 Chapter V.--ELECTRICAL APPARATUS. What is electricity?--Forms of electricity--Magnetism--The permanent magnet--Lines of force--Electro-magnets--The electric bell--The induction coil--The condenser--Transformation of current--Uses of the induction coil 112 Chapter VI.--THE ELECTRIC TELEGRAPH. Needle instruments--Influence of current on the magnetic needle--Method of reversing the current--Sounding instruments--Telegraphic relays--Recording telegraphs--High-speed telegraphy 127 Chapter VII.--WIRELESS TELEGRAPHY. The transmitting apparatus--The receiving apparatus--Syntonic transmission--The advance of wireless telegraphy 137 Chapter VIII.--THE TELEPHONE. The Bell telephone--The Edison transmitter--The granular carbon transmitter--General arrangement of a telephone circuit--Double-line circuits--Telephone exchanges--Submarine telephony 147 Chapter IX.--DYNAMOS AND ELECTRIC MOTORS. A simple dynamo--Continuous-current dynamos--Multipolar dynamos--Exciting the field magnets--Alternating current dynamos--The transmission of power--The electric motor--Electric lighting--The incandescent lamp--Arc lamps--"Series" and "parallel" arrangement of lamps--Current for electric lamps--Electroplating 159 Chapter X.--RAILWAY BRAKES. The Vacuum Automatic brake--The Westinghouse air-brake 187 Chapter XI.--RAILWAY SIGNALLING. The block system--Position of signals--Interlocking the signals--Locking gear--Points--Points and signals in combination--Working the block system--Series of signalling operations--Single line signals--The train staff--Train staff and ticket--Electric train staff system--Interlocking--Signalling operations--Power signalling--Pneumatic signalling--Automatic signalling 200 Chapter XII.--OPTICS. Lenses--The image cast by a convex lens--Focus--Relative position of object and lens--Correction of lenses for colour--Spherical aberration--Distortion of image--The human eye--The use of spectacles--The blind spot 230 Chapter XIII.--THE MICROSCOPE, THE TELESCOPE, AND THE MAGIC-LANTERN. The simple microscope--Use of the simple microscope in the telescope--The terrestrial telescope--The Galilean telescope--The prismatic telescope--The reflecting telescope--The parabolic mirror--The compound microscope--The magic-lantern--The bioscope--The plane mirror 253 Chapter XIV.--SOUND AND MUSICAL INSTRUMENTS. Nature of sound--The ear--Musical instruments--The vibration of strings--The sounding-board and the frame of a piano--The strings--The striking mechanism--The quality of a note 270 Chapter XV.--WIND INSTRUMENTS. Longitudinal vibration--Columns of air--Resonance of columns of air--Length and tone--The open pipe--The overtones of an open pipe--Where overtones are used--The arrangement of the pipes and pedals--Separate sound-boards--Varieties of stops--Tuning pipes and reeds--The bellows--Electric and pneumatic actions--The largest organ in the world--Human reeds 287 Chapter XVI.--TALKING-MACHINES. The phonograph--The recorder--The reproducer--The gramophone--The making of records--Cylinder records--Gramophone records 310 Chapter XVII.--WHY THE WIND BLOWS. Why the wind blows--Land and sea breezes--Light air and moisture--The barometer--The column barometer--The wheel barometer--A very simple barometer--The aneroid barometer--Barometers and weather--The diving-bell--The diving-dress--Air-pumps--Pneumatic tyres--The air-gun--The self-closing door-stop--The action of wind on oblique surfaces--The balloon--The flying-machine 322 Chapter XVIII.--HYDRAULIC MACHINERY. The siphon--The bucket pump--The force-pump--The most marvellous pump--The blood channels--The course of the blood--The hydraulic press--Household water-supply fittings--The ball-cock--The water-meter--Water-supply systems--The household filter--Gas traps--Water engines--The cream separator--The "hydro" 350 Chapter XIX.--HEATING AND LIGHTING. The hot-water supply--The tank system--The cylinder system--How a lamp works--Gas and gasworks--Automatic stoking--A gas governor--The gas meter--Incandescent gas lighting 386 Chapter XX.--VARIOUS MECHANISMS. Clocks and Watches: --A short history of timepieces--The construction of timepieces--The driving power--The escapement--Compensating pendulums--The spring balance--The cylinder escapement--The lever escapement--Compensated balance-wheels--Keyless winding mechanism for watches--The hour hand train. Locks :--The Chubb lock--The Yale lock. The Cycle :--The gearing of a cycle--The free wheel--The change-speed gear. Agricultural Machines :--The threshing-machine--Mowing-machines. Some Natural Phenomena :--Why sun-heat varies in intensity--The tides--Why high tide varies daily 410