394

Rias, 313

Richter, Prof., 308–310
Richthofen, Baron, 261
Rio Janeiro, 330

River cliffs, recession of, 61, 63
Rivers, change of course, 108

- direction of, not influenced by faults
and flexures, 57, 156, 165
erosion by, 59

flowing in direction of dip, 77, 80
- flowing in direction of strike, 75
geological action of, 34
longitudinal, 107

older than mountains they traverse,
46, 57

- original course, determined by sur-
face-slope, 56, 74, 77, 104, 120,
131, 137, 351, 353
terraces of, 7, 51

underground, 268

valleys, eroded by, 350, 357

Roches moutonnées, 222, 234, 288, 301,
383

Rock basins, 222, 288, 293
Rock-fall basins, 284
Rock-falls, 119

Rock-flexures, infraglacial, 236

Rock-flour, 215

Rock-forming minerals, 20

Rock-removal, evidence of, 13

Rock-salt, 23, 266

Rock-shattering, infraglacial, 221
Rock-shelters, 276

Rocks, chemical composition of, 20
classes of, 3, 4, 19

comparative resistance of, to denu-
dation, 44, 77, 78

disintegration of, 23-26, 198

porosity of, 21

shattered by frost, 29

Rodgers, Prof., 118
Rotted rock, 27

Rubers Law, 136

Rügen, 234
Rule Water, 136
Rumpfgebirge, 170, 380
Russia, black earth, 263
ground-moraines, 238
lakes, 286

Saddlebacks, see Anticlines.
Sahara, 251