7H 



INDEX 



Scutella aberti, 627. 



Sea arches, 210. 



Sea-captured streams, 214. 



Sea caves, 209. 



Sea cliffs, erosion by waves, 208. 



by weather, 208. 

 Sea cucumbers, 415. 

 Seattle, lowering of hill at, 84. 

 Sea urchins, Carboniferous, 480. 



Ordovician, 431. 

 Sedimentary rocks, 23. 



classification of, 249-250. 



influence upon topography, 250. 

 Sediment of streams, how carried, 81. 



source of, 81. 

 Sediments, cementation of, 248. 



consolidation of, 248. 



effect of heat on, 249. 



effect of pressure on, 248. 

 Seismographs, 287. 

 Seminula argentea, 482. 



subquadrata, 482. 

 Septaria, JJ. 

 Sequoia gigantea, 632. 

 Sequoias, 632-633. 

 Seracs on glaciers, 148. 

 Serpentine, 690. 

 Shaler, N. S., 303. 

 Shales, 250. 

 Sharks, Devonian, 462-463. 



Mesozoic, 533. 

 Shetland Islands, work of wind in, 44. 

 Shingle, 217. 



Shoal-water deposits, 237-241. 

 Shore currents, 200. 



deposition by, 219, 223-224, 233. 



transportation by, 217. 

 Shore ice, 203. 

 Shore line, cycle of erosion of, 231-233. 



rough, 226. 



smooth, 224. 

 Shores, maturity of, 232. 



rough, 226. 

 Shoulders, 165. 

 Siderite, 686. 



Sierra Nevada Mountains, 513, 582. 

 Sigillaria, 494-495, 497. 

 Silicate minerals, 689-690. 

 Sills, 326-327. 



Sill tunnel, Austria, rapid erosion of, 96. 

 Silurian period, 401, 439-451. 



climate of, 451. 



close of, 451. 



Silurian period — {Continued) 



deserts of, 443. 



duration of, 451. 



formations, character of, 440-442. 

 thickness of, 442. 



life of, 444-450. 



migration during, 451. 



of New York state, 439. 



in other continents, 444. 



oscillations of level during, 441. 



physical geography of, 439-442. 



volcanic activity of, 444. 

 Silver Spring, Fla., 63, 65. 

 Slate, 344-345- 

 Slickensides, 268. 

 Slip, 262. 



Slope of ice sheets, 647-648. 

 Sloths, 621, 670. 

 Slumping, 73. 

 Smith, J. P., 528. 

 Snakes, 624. 



Snow crystals, growth of, 143. 

 Snow fields, 142. 

 Snow line, 141. 

 Sogne fiord, Norway, 166. 

 Soil, creep of, 31, 71. 



kinds of, 42. 



removal of, 43. 

 Solfataras, 323. 

 Solution by ground water, 60. 



by streams, 83. 



in disintegration of rocks, 35, 36. 

 Sphalerite, 687. 

 Sphenophycus latifolius, 436. 

 Sphenophylls, 495. 

 Spherical concretions, 77. 

 Spheroidal weathering, 39, 40. 

 Spirifer acuminatus, 458. 



cameratus, 482. 



disjunctus, 458. 



mucronatus, 458. 



radiatus, 446. 

 Spiriferina, 526. 

 Spiriferina spinosa, 482. 

 Spirifers, 457. 

 Spirula, 531. 

 Spits and bars, 220. 

 Sponges, Cambrian, 416. 



Mesozoic, 524. 



Ordovician, 427. 



Proterozoic, 397. 



Silurian, 445. 

 Spouting horns, 210. 



