348. Micrometer free wheel, 441. Micro-photography, 265. Microscope, 254; compound, 261, _263_; in telescope, 257; simple, _254_. Mineral oil, 392. Mirror, parabolic, 261, _262_; plane, _267_. Morse, 132, 145; code, 128; inker, 142; sounder, 132. Telegraphy, high-speed, 135; wireless, 137.