494 
Ice stream, 196, 197, 204. 
Ichthyornis, 434. 
Ichthyosaurus, 430, 433. 
Igneous rocks, 52, 54; age of, 403; clas- 
sification of, 64, 66; distribution of, 
70; joint planes in, 278; metamor- 
phism by, 372; ores near, 384; struct- 
ure of, 65; texture of, 57; variation 
in composition of, 64. 
Infusoria, 38. 
Infusorial earth, 91, 97. 
Insects, Carboniferous, 422; Devonian, 
417; Ordovician, 410; Silurian, 414. 
Interior of earth, heat of, 20. 
Intrusive igneous rocks, 55, 62, 66, 347; 
metamorphism by, 372. 
Intruded sheets, 348. 
Invertebrates, era of, 402. 
Inverted folds, 286, 288. 
Iron, 24, 28; cementing by salts of, 275; 
deposits of salts of, 97; native, 379; 
ores of, 47, 86, 383; ores of Clinton 
beds, 455; veins of, 97. 
Iron pyrites, 47, 49. 
Isoseismal lines, 354, 355. 
J 
Japan, change in level of, 295; earth- 
quake in, 355, 357, 358, 360; moun- 
tains of, 319; volcanoes of, 341. 
Joint planes, 277; aid of, in weathering, 
125; cause of, 279; in igneous rocks, 
278; ores in, 380; passage of water 
along, 146; regularity of, 282; in sedi- 
mentary rocks, 277. 
Jupiter Serapis, 294. 
Jurassic, 402, 462. 
Juratrias, 398, 402 ; climate of, 464 ; geog- 
raphy of, 464; life of, 426. 
K 
Kaolin, 41, 81, 373. 
Kilauea, 341, 342. 
Krakatoa, 339, 343, 360. 
L 
Labrador current, 236. 
Laccolites, 348. 
ELEMENTARY GEOLOGY 
Lakes, animal deposits in, 189, 194; 
burial of fossils in, 389; cause of, 188, 
219, 484; chemical deposits in, 193, 
194 ; of Cordilleras, 469, 471, 474; deltas 
in, 182; dried, 475; erosion in, 237; 
plant deposits in, 190, 194; salt, 475; 
sediment in, 188, 194. 
Lamine, 260. 
Lamination, 262. 
Lamellibranchs, Carboniferous, 419 ; De- 
vonian, 415; Eocene, 437, 489; Meso- 
Zoic, 426, 428, 432; Neocene, 440, 441. 
Land, changes of level of, 294, 472; 
movement of, 300. 
Landslips, 143, 145. 
Lateral moraine, 204, 218. 
Laurentian, 402, 404. 
Lava, 53-56, 329, 332, 334, 340; aid in 
ore accumulation, 384; crystallization 
of, 58; flowing of, 69; metals in, 378; 
perservation of fossils by, 389; Trias- 
sic, 466. 
Lava flow, 56. 
Lava, sheets of, 345. 
Lenticular form of strata, 266. 
Lepidodendrons, Carboniferous, 460. 
Level of land, changes in, 294. 
Lichens, aid in weathering, 114, 115. 
Life of Cambrian times, 407; of Car- 
boniferous, 419; of Cenozoic, 4383; 
coming of, 446; of Devonian, 414; 
earliest, 405; of Mesozoic, 426; of 
Ordovician, 408; of Paleozoic, 406; 
progress of, 397; of Silurian, 410. 
Life record, imperfection of, 391. 
Lignite, 93. 
Limestone, 29, 48, 81, 88, 89, 90, 92, 97, 
99, 105, 454, 455, 457; beds of, 251; 
caves in, 140, 150; deposit in lakes, 
192, 194; deposit of, in sea, 287, 259; 
metamorphism of, 366, 370, 375; solu- 
tion of, 140, 150, 221. 
Limonite, 48. 
Lipari Islands, 339. 
Loess, 80, 131, 138. 
Luray Cave, 141, 143. 
M 
Magnesian limestone, 44, 86. 
Magnesium, 24, 30. 
