Two principal types of boilers--Aids to combustion--Boiler fittings--The safety-valve--The water-gauge--The steam-gauge--The water supply to, 39; water-tube, 21. Brakes, hydraulic, 188; motor car, 105. Gearing of cycle, 439. Glaisher, 348. Gland, 50, 363. Glass, flint and crown, 242. Going-barrel for watches, 415. Gooch reversing gear, 65. Governors, speed, 67; of motor.