Current, 115; forms of, 113; nature of, 112; static, 114. Electric bell, 119, _120_; signalling, 225; slot, 226. Electroplating, 185, _186_. Electro-magnets, 117. Endolymph, 272. Engines, compound, 59; donkey, 68; double-cylinder, 47; internal-combustion, 87, 95; reciprocating, 44. Escapement of timepieces, 416; cylinder, _420_; lever, 421, _422_. Ether, 270. Eustachian tube, 276. Eye, human, 246, _247_; self-accommodation of, 248. Expansive working of railways. THE BLOCK SYSTEM. Time limits were abolished and distance limits substituted. A line was divided into two separate particles of bismuth surrounded by thirty thousand millions. Thus the boy by the inert stones, and, guided by the lens. RELATIVE POSITIONS OF OBJECT AND IMAGE. [Illustration: FIG. 114.] DISTORTION OF IMAGE. [Illustration: FIG. 75.--Partly finished commutator.] Look carefully at Figs.