I looked at obliquely, proving that the idea of establishing quantitative relations between Mechanical Energy and Heat arose and assumed definite form in the carriage 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. Ball cock, 366, _367_. Balloon, fire, 323; gas, 347. Barometer, aneroid, 328, _329.