CHAPTER V.. The Work of Snow and Ice.

THE WORK OF SNOW AND ICE.

+Snow- and Ice-fields+ 244 The passage of snow into névé and ice, 246. Structure of the ice, 247. Texture, 247. Inauguration of movement, 248.

+Types of Glaciers+ 251

+The General Phenomena of Glaciers+ 256 Dimensions, 256. Limits, 258. Movement, 259. Conditions affecting rate of movement, 261. Likenesses and unlikenesses of glaciers and rivers, 262.

+Surface Features+ 266 Topography, 266. Surface moraines, 266. Relief due to surface débris, 268. Dust-wells, 269. Débris below the surface, 272.

+Temperature, Waste, and Drainage+ 273 The winter wave, 274. The summer wave, 276. The temperature of the bottom, 276. Temperature of the interior of the ice, 277. Compression and friction as causes of heat, 278. Summary, 279. Movement under low temperature, 279. Evaporation, 279. Drainage, 280.

+The Work of Glaciers+ 281 Erosion and Transportation 281 Getting load, 282. Conditions influencing rate of erosion, 283. Summary, 286. Varied nature of glacial débris, 286. The topographic effects of glacial erosion, 287. Fiords, 290. The positions in which débris is carried, 290. Transfers of load, 292. Wear of drift in transit, 298. Deposition of the Drift 298 Beneath the body of the ice, 298. At ends and edges of glaciers, 299.

+Types of Moraines+ 301

The terminal moraine, 301. The ground moraine, 301. The lateral moraines, 302. Distinctive nature of glacial deposits, 304. Glaciated rock surfaces, 304.

+Glacio-Fluvial Work+ 305

+Icebergs+ 307

+The Intimate Structure and the Movement of Glaciers+ 308 The growth and constitution of a glacier, 308. The arrangement of the crystal axes, 312. The Probable Fundamental Element in Glacial Motion 313 Melting and freezing, 313. Accumulated motion in the terminal part of a glacier, 316. Auxiliary Elements 317 Shearing, 317. High temperature and water, 318. Applications, 319. Corroborative Phenomena 320 Other Views of Glacier Motion 321