Helmet, _336_; lamp, _338_. Donkey-engines, 68. Doorstop, self-closing, 344. Double-cylinder engines, 47. Draught, forced, 28, _29_; induced, 29. Drum and fusee, _414_. Durability of motor-car engine, 96. D-valve, 67. Dynamo, alternating, 164, 174; brushes, _172_; compound, 174; continuous-current, 165; multipolar, 169; series wound, _173_; simple, 161, _162_. Ear, the, _271_, _273_; a good, 274, 307; sensitiveness of, 275. Eccentric, _52_, 53; setting of, 53. Sliders, 297. Sound, nature of, 230; propagation of, 231. Li Hung Chang, 157. Lindsay, James Bowman, 145. Lines of Force.' It is needless to dwell for a.