_327_. Beau de Rochas, 89. Bell, diving, _332_; electric, 119, _120_. Bellows of organ, 296; board of piano, 280. Spagnoletti disc instrument, 212. Sparking-plug, _102_. Spectacles, use of, 249. Spectrum, colours of, 230. Speed governors, 67, _68_, _69_; Hartwell, 70; marine, 71. Speed of motor.