
INDEX 
Necks, 196, 301 ; origin of, 199 
Nepheline, 14 ; -basalt, 51, 89 
Nephelinite, 52 
Neutral rocks (igneous), 40 
New Zealand, 229, 265 
Nickel-iron, in igneous rocks, 229 
Nickel ores, 249, 263 
Nile Valley, 391, 411 
Nodules, 120 
Nordmarkite, 46 
Norite, 49 
Normal faults, 157, 171, 295, 304 
Normal folds, 135 
North America, lakes 
423 
North Downs, 410 
Norway, ore-formations of, 229, 235, 
265 
Nosean, 14 
Novaculite, 76 
of, 419, 422, 
OBLIQUE bedding, 115 ; faults, 165 
Obsidian, 44, 49, 85, 89 
Ochil Hills, rgt 
Oil shale, 62, 72 
Old red sandstone, 147 
Oligoclase, 12, 13 
Olivine, 21 ; -gabbro, 49 ; -dolerite, 50 ; 
-norite, 49; -rocks, 52 
Omphacite, 18 
Onega, Lake, 419 
Onyx, 5 
Odlite, 65, 70, 84; Lower, of England, 
IIS 
Odlitic iron-ore, 67 
Opal, 5 ; varieties of, 6 
Ophitic structure, 50 
Orbicular diorite, 48, 124 
Ore-formations, 228; origin of, 266; 
prospecting for, 335 
Ores, in igneous rocks, 229; in bedded 
rocks, 231; as precipitates from 
aqueous solutions, 231; as clastic- 
formations, 232; in schistose rocks, 
234, 257; in lodes, etc., 237; quasi- 
bedded, 255 
Organically derived rocks, 68 
Original minerals, 37 
Original mountains, 394 ; valleys, 413 
439 
Orthoclase, 10, 11; -porphyry, 46, 87, 
89 
Orthophyre, 46 
Outcrop of strata, 130; concealed, 131, 
290, 308; width of, affected by dip, 
131, 363; width of, affected by form 
of surface, 132; affected by faults, 
158 ; tracing of, 281 ; forms of, 291 
Outliers, 176 
Overfolds, 137 
Overlap, 183, 294 
Overthrusts, 174, 298 
Ovifak, Greenland, 229 
Oxford clay, 115 
Oxides, 2; metallic, in igneous rocks, 
229 
PAMPAS, 412 
Paragenesis of ores, 249 
Parallel roads of Glenroy, 316 
Parrot coal, 71 
Peat71; 3169 
Pegmatite, 42 ; -veins, 207 
Pegmatitic structure, 42 
Pencil-slate, 76 
Perched blocks, 314 
Peridote, 21 
Peridotites, 52, 89 
Perimorphs, 6, 37 
Perlite, 34, 45 
Perlitic structure, 34, 45 
Permeation of fossils, 92 
Permian copper ores, 263 
Peru, 261 
Petrifaction, 92 
Petroleum, 72 
Phacoids, 77, 226 
Phenocrysts, 35, 36 
Phonolite, 47, 86, 87, 89 
Phosphates, 30 
Phosphatic nodules, 73 
Phosphorite, 31 
Phyla of animal kingdom as represented 
by fossils, 96 
Phyllite, 77 
Picotite, 8 
Picrite, 52 
Pipe-clay, 62 
Pipes of ore, 259 
Pisolite, 65 
