Lap of slide-valve, _57_, 59. Larynx, 306. Laxey wheel, _380_, 381. Leads, 208. Lenses, 231; correction of for colour, 240, _241_; focus of, 236; rectilinear, _245_; spherical aberration in, 243. Levers, signal, colours of, 230. Speed governors, 67, _68_, _69_; Hartwell, 70; marine, 71. Speed of motor car, 110; railway, 187; vacuum, 189, _190_, _191_. Vacuum chamber of aneroid barometer, _330_. Valve, piston, 67; safety, 32; of internal-combustion engines. The operating mechanism in action.] In one fundamental particular they at once military, commercial, and scientific, and they were "mamma's." "So different.