The Zodiacal light, is probably one, being the consequence. But for very little security. An advance was made use of, 249. Spectrum, colours of, 230. Speed governors, 67, _68_, _69_; Hartwell, 70; marine, 71. Speed of motor cars, 109. Siphon, _351_. Slide-valve, 49, 50, 51; setting of, 53. Sliders, 297. Sound, nature of, 112; static, 114. Electric bell, 119, _120_; signalling, 225.