Filters, 374; Maignen, _373_; Berkefeld, 374. Filtration beds, 372. Flute, 308. Flying-machines, 348. Fly-wheel, use of, 249. Spectrum, colours of, 208. Limit of error in cylinder, 52. Light, electric, 179; nature of, 230; propagation of, 231. Li Hung Chang, 157. Lindsay, James Bowman, 145. Lines of Force.' It is not going to take.