IjS^DEX 



397 



Psilomelane, 101 



Puddingstone, 115 



Pulaskite, 75 



Pumice, origin of, 57 



Pyrite as a roek constituent, 2Q 



decomposition of, 165 

 Pyrolusite, 101 

 Pyrophyllite, 109 



Pyroxene altered to serpentine, 107 

 Pyroxenes as rock constituents, 20 

 Pyroxenites, tlie, 93 



chemical composition of, 94: 



classification of, 94 



colors of, 94 



mineral composition of, 93 



nomenclature of, 94 



structure of, 94 



Quartz, 104 



as a rock constituent, 12 

 pebbles, solution of, 172 

 porphyry, classification of, 66 

 color of, 65 

 composition of, 65 

 nomenclature of, 66 

 structure of, 65 

 -free porphyries, 71 

 Quartzite boulders, weathering of, 

 237 

 chemical composition of, 149 

 origin of, 137 

 Quitman Mountains, weathering in, 

 161 



Rainfall, amount reaching soil, 267 



Kegolith, the, 287 



Eegur, 372 



Eesiduary deposits, 289 



chemical composition of, 



294 

 inherited characteristics, 



291 

 mechanical analyses, 296 

 physical properties, 291 

 Rhodochrosite, 106 

 Rhombporphyry, 71 

 Rhyolite, defined, 68 



origin of name, 68 

 River, channels formed by weather- 

 ing, 229 

 water, amount of mineral mat- 

 ter in solution in, 171 

 Rivers, transporting power of, 309 

 Rock-forming minerals, list of, 11 

 Rocking boulders, 238 

 Rock classification, 53 

 Rocks, chemical composition of, 41 

 color of, 42 



Rocks, conductivity of, 162 

 definition of, 1 



formed as sedimentary deposits, 

 112 

 through chemical agencies, 

 99 

 igneous agencies, 55 

 fracture of, 44 

 kinds of, 52 

 igneous, 55 



how to be studied, 60 

 lustre of, 44 

 mode of occurrence, 45 

 oldest known, 45 

 original constituents of, 10 

 physical and chemical proper- 

 ties of, 30 

 relationship of plutonic and 



effusive forms, 59 

 secondary constituents of, 10 

 specific gravity of, 40 

 structure of, 30 

 structural features dependent on 



conditions of cooling, 56 

 temperatures at varying depths, 



162 

 thin sections of, 35 

 Rock weathering, see under weather- 

 ing, 150 

 defined, 151 

 Roots, corrosive action of, 181 

 depth of penetration, 180 



Salt, distintegration through crys- 

 tallization of, 177 

 water marsh deposits, 324 

 Sand dunes, 283, 334 



lithologieal nature of, 334 

 rate of movement, 334 

 types of, 329 

 Sands, ^olian, 283, 334 



beach, 329 

 Sandstones, 114 



cementing material of, 114 

 composition of, 115 

 Sandstone, spheroidal weathering of, 

 233 

 weathering of, 213 

 Santa Rosa Island, sand of, 329 

 Saxonite, 92 

 Schists, the, 146 



chemical composition of, 149 

 mineral composition of, 146, 147 

 origin of, 148 

 weathering of, 234 

 Seacoast swamp deposits, analyses 

 of, 327 

 formation of, 342 



