Melbourne Observatory, great reflecting telescope, 312, 313, 337; composition and production of specula, 120, 121, 129; view of optical part, 143; mode of mounting speculum, 144-149; photographs of the moon, 459 Mercurial pendulum, 187, 188, 192 Mercury, in Ptolemy’s system, 3; in Tycho Brahe’s, 46; as a telescopic object, 350 Meridian, defined by Euclid, 12 Meridional observations, first employment of, 20 Meridian of Greenwich, 252 Meridian circle, the first, 20; at Cambridge (U.S.), 248 Meridians of longitude (_see_ Longitude) MERIDIONAL OBSERVATIONS, MODERN (Book IV.), 233-290 Merz (M.), manufacture of flint-glass discs, 119; cost of large object-glasses, 172; large telescopes, 303 Metallic specula, 120, 171 Meton, meridian observations by, 25 Meudon Observatory, solar photography at, 470 MICROMETER, THE (Chap. XV.), 218-232; wire micrometer, 221, 352; heliometer, 224; double image, 229; position, 353; measurements made by, 355, 359-366, 368 Microscopes, for reading transit circles, 247; for Newall’s telescope, 307 Middlesborough, time signal, 278 Milky Way, observations of Euclid, 11 Miller, spectrum analysis, 410 Mirrors, concave and convex, 94-98 Mirrors for reflecting telescopes (_see_ Specula) MODERN MERIDIONAL OBSERVATIONS (Book IV.), 233-290 Molecular vibration, 373, 401, 410, 429, 449, 450 Months, first observations of, 5 Moon, The, in Ptolemy’s system, 3; motions observed by the Chaldeans, 4; parallax observed by Ptolemy, 35; used by Hipparchus to determine longitude, 44; as a telescopic object, 350; the lunar crater, Copernicus, 354; measurement of shadow thrown by a lunar hill, 355; photographs and stereographs, 459, 464, 465, 466; part of Beer and Mädler’s map, 476; of De La Rue’s photograph, 477 MOUNTING OF LARGE TELESCOPES (Chap. XX.), 293-327 Mounting of specula for reflecting telescopes, 144, 149, 169 Mudge, grinding and polishing specula, 129; gravity escapement, 200 Mural circle, 241, 242 Mural quadrant, Tycho Brahe’s, 233, 235 Multiple stars, 351 N. Nebulæ, 351 Nebula of Orion, 157, 158 Neptune, as a telescopic object, 351 Newall’s equatorial refractor, 302; with spectroscope, 427; flint-glass discs for, 119; production of discs for object-glass, 128; photographs of the moon, 459 Newcastle, time signals, 278 Newton (Sir Isaac), on refracting telescopes, 82; his reflecting telescope, 101, 102; use of pitch in polishing specula, 128; refrangibility of light, 387; polarized light, 442 Newtonian reflector, 149; view of optical part, 143; effective light, 169; Grubb’s form, 303; Browning’s form, 304; mounting of, 310 Nicols’ prism, 115; measurement of the light of stars, 380; polarization of light, 443, 447, 448, 449, 450 North pole, diagram illustrating how it is found, 249, 251 O.