Result. I think of for colour, 240, _241_; focus of, 236; rectilinear, _245_; spherical aberration in, 243. Levers, signal, colours of, 208. Limit of error in cylinder, 52. Light, electric, 179; nature of, 270; board of piano, 283. Advancing the spark, 102. Air-gun, _342_. Air-pump for cycle tyres, _340_; for Westinghouse brake, 199. Alternating currents, 164; dynamo, 164. Amperage, 125. Angle of advance, 57, 58; incidence, 268; reflection, 268. Aorta, 360. Arc lamp, 182. Archimedes, 412. Armature, 162. Arteries, 358. Arterial blood, 359. Atmospheric pressure, 350. Auditory nerve, 272. Automatic brakes, 188; signalling, 228; stoker, 399. Backfall, 298. Balance-wheel, 419.