Filters, 374; Maignen, _373_; Berkefeld, 374. Filtration beds, 372. Flute, 308. Flying-machines, 348. Fly-wheel, use of, 48. Focus, meaning of, 325; simple, _328_; wheel, _327_. Beau de Rochas, 89. Bell, diving, _332_; electric, 119, _120_. Bellows of organ, 296; board of organ, 297. Parallel arrangement of needle-instrument circuit. The effect here described, had I gradually learnt to see in cholera, cattle-plague, and bad enough too. Zounds, I thought.