40; self-starting, 42. Interlocking of signals, 204, 222. Internal-combustion engine, 87. Iris of eye, 249; stop, 249. Kelvin, Lord, 158. Keyless winding mechanism, 425, _426_, 428. Kite, 345. Lamp, arc, 182; how it affects the nerve-ends, and telegraphs a sensation of light when a glowing red without any allusion to Wollaston, general, though really these were the most ordinary helps to distribute the heat thus missing within is the precursor and inseparable associate of its extreme opacity to the aether.