Extension, a property of matter, [44]
Eye, description of, [353]
Eye, images in, inverted, [356]
Feathers, how a non-conductor of heat, [305]
Fire-engine, [179]
Flexibility, [29]
Flies, feet of, [157]
Force, relation of, to velocity, [194]
Forcing-pumps, [178]
Franklin, his theory of electricity, [373]