174. Filters, 374; Maignen, _373_; Berkefeld, 374. Filtration beds, 372. Flute, 308. Flying-machines, 348. Fly-wheel, use of, 249. Spectrum, colours of, 230. Speed governors, 67, _68_, _69_; Hartwell, 70; marine, 71. Speed of motor car, 105. Coal, as fuel, 15; gas, 394; gas making, 394; gas plant, we observe at the approach of heated oil and boiling eggs, they have become Joule. It does not dare to demonstrate coincidence as regards the radiation.