rs, 17;
torsion balance, 261;
star systems, 426

Michelson, velocity of light, 241

Milky Way, grindstone theory, 14;
clustering power, 20, 26;
structure, 20, 41, 45, 47, 423-425;
centre of gravity, 40, 41;
frequented by Wolf-Rayet, temporary, and helium stars, 380, 399, 425;
by gaseous nebulae, 402;
drawings and photographs, 424, 425

Miller, W. A., spectrum analysis, 132, 136, 137;
stellar chemistry, 373

Mira, light changes, 10;
spectrum, 374, 379

Mitchel, lectures at Cincinnati, 6

Mitchell, photograph of reversing layer, 190

Moeller, theory of Faye's comet, 98

Mohn, origin of comets, 370

Moll, transit of Mercury, 245

Monck, Perseid meteors, 341;
new stars, 395

Moon, acceleration, 2, 271, 272;
magnetic influence, 130;
photographs, 152, 153, 268;
solar parallax from disturbed motion, 230, 240;
study of surface, 263;
atmosphere, 263-265;
charts, 265-267;
librations, 266;
superficial changes, 267, 268;
thermal radiations, 269, 270;
rotation, 272;
tables, 272, 273;
origin, 316-318

Morinus, celestial chemistry, 140

Morstadt, Andromede meteors, 332

Mouchez, photographic survey of the heavens, 413;
death, 414

Mueller, phases of Mercury, 246;
of minor planets, 288;
albedo of Mars, 283;
of Jupiter, 290;
of Saturn, 303;
variability of Neptune, 305;
of Pons's comet, 366;
stellar photometry, 421

Munich, Optical Institute, 28, 34

Myer, solar eclipse, 183

Nasmyth, Lassell's reflector, 83;
solar willow-leaves, 164;
comparative lustre of Mercury and Venus, 255;
condition of Jupiter, 289

Nasmyth and Carpenter, _The Moon_, 265

Nebula, Andromeda, early observations, 21;
new star in, 394, 395;
photographs, 395, 409;
structure, 396;
spectrum, 402, 403;
visibility at Arequipa, 435

Nebula, Orion, observed by Herschel, 12;
mentioned by Cysatus, 21;
apparent resolvability, 119;
suspected variability, 403;
radial movement, 405;
spectrum, 407;
photographs, 407, 408, 436

Nebulae, first discoveries, 22;
catalogues, 22, 46, 50, 412;
distribution, 23, 48, 422;
composition, 24, 47, 401, 402;
resolution, 47, 117, 119;
double, 48, 412;
spiral, 118, 410, 412;
new stars in, 394-396, 399, 401;
spectra, 401-403, 407;
va