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INDEX.
prevalent in Scotland and Ireland, 119. Physical geography of, 120. Igneous rock of, 121. General inferences to he deduced from a consideration of the whole subject, 122.
Gneiss, proportion of oxygen in, i. 25. Rare in the Harz, Cornwall, and Wales, 58. Metamorphism of, how effected, ii. 143.
Golt, how and where found, i. 233, et seq.
Gordian Medal, discovery of a, at Groningen, ii. 65.
Graham, Mrs., her account of the first Chilian earthquake, ii. 214.
Graham's Island, its volcanic phenomena, ii. 214.
Grampians, dip of stratified rocks in the, i. 37. Hypozoic strata predominant in, 58. Afford an example of the granitic basis of the earth's crust, 108. Picturesque beauty of, 133, 134. Once uplifted, 151. Gneiss mountains of, ii. 321.
Granite, proportion of oxygen in, i. 25. Its composition, 25. The basis of the earth's crust, 10S. Veins of, in Glen Tilt, Cornwall, &c., 109. 121. Its rapid decomposition by carbonic acid gas, ii. 9. May have been derived from fusion of previously formed strata, 72. Once a melted fluid, 79. Great protuberances of, in the valley of theJValteline, 88. Composition of, 92. Huttonian theory of the crystallisation of, 101. Alterations produced by the proximity of, to various strata, 101, et seq. Age of, how determined, 148. Basis of the trachytic masses of Mexico, 230.
Grauwacke system. See Palæozoic Strata, Clay Slate System. Origin of the term and its application, i. 126.
Gravel, various theories accounting for the origin of, i. 298. 302. Not necessarily of diluvial origin, 301. Sir R. Murchison's examination of the Welsh border accounting for deposits of, in vales of the Dee and Severn, 301. Geographical circumstances accounting for distribution of, 301. Local origin of some sorts of, 302. Problems suggested by these theories, important for a correct view of the origin of diluvial accumulations, &c., 302. Banks of, 341.
Green sand, how and where found, i. 234. See Cretaceous System.
Green stone, how and where found, i. 121. 208.
Greenhow Hill, disturbed strata of, i. 44.
Greystone, how found, ii. 84.
Griffith, Mr., on fissures, i. 65. His map, 178. On colour of slaty rocks of S. E. Ireland, ii. 143.
Grit, millstone, an important deposit in the north of England, i. 180.
Group, erratic block, i. 281. 283.
Guadaloupe, earthquake of, ii. 246.
Guanaxiato, mines of, their temperature, ii. 272.
"Guide to Geology," references to, i. 128. 137.
Gypsum of the Triassic system, where found, i. 204. Its origin, 210.
H.
Hall, Sir James, his experiments on powdered limestone, ii. 79. His examination of mountain of Tornideon, 102. His examination of the Huttonian doctrine of the induration of rocks by heat, 129. Quotation from his "Geology of New York," i. 143.
Ham, Mr., his analysis of the waters of the Severn, ii. 34.
Hamilton, Sir W., on the eruption of Vesuvius, ii. 235.
Harcourt, Mr. W. V., his experiments on the effects of long-continued heat, i. 126. His geological investigations, ii. 42. 50.
Hardrow Force, i. 177.
Harlech sandstones, i. 130.
Harz Mountains, mica schist and gneiss of rare occurrence in, i. 58. Elevation of the, 153.
Hasenberg, basalt of, ii. 95.
Hatfield Chase, extent and drainage of, ii. 65.
Hawaii or Owhyhee, volcanic crater at, ii. 232.
Headon Hill, limestones of, i. 251.
Heat, Mr. Harcourt's experiments on effects of long-continued, i. 126. Its effects on rocks, ii. 72. 111. Its modern effects on the globe, 200. Hot springs and volcanos indicative of the presence and degree of, 200. See Volcanos, Thermal Springs, Earthquakes. Dependent on the calorific influence radiated from the sun, 263. 266. This influence
