earthquakes, 731.
----, plants drifted to sea by, 745.

Hurst Castle shingle bank, 318.

Hutchinson, John, his "Moses's Principia," 33.

Hutton, distinguished geology from cosmogony, 3.
----, on igneous rocks and granite, 51.
----, represented oldest rock as derivatives, 52.

Huttonian theory, 51, 57.

Hybrid races, Lamarck on, 572.
----, animals, 600.
----, plants, 602.

Hydrogen, deoxidating power of, 547.
----, flame of; seen in eruption of Vesuvius, 378.
----, why not found in a separate form among volcanic gases, 548.

Hydrophytes, distribution of, 617, 623.

Hydrostatic pressure of ascending lava, 416, 553.

Hypogene rocks, 178.

Hyracotherium, Eocene mammifer, 142.

Hythe, encroachments of sea at, 316.

I.

_Ianthina fragilis_, its range, &c., 650.

Ice, animals imbedded in, 83.

Ice of rivers, transporting power of, 219.
----, drift, influence of, on temperature, 95.
----, predominance of, in antarctic circle, 98.
----, formation of field, 107.
----, transportation of rocks by, 155, 219, 521.

Icebergs, formation of, 96, 97.
----, distance to which they float, 100, 227.
----, limits of glaciers and, 228.
----, plants and animals transported by, 622, 639.
----, action of, when stranded, 228.
----, rocks transported by. _See_ Ice.
----, floating in Northern hemisphere, 86.
----, not all formed by glaciers, 228.

Iceland, icebergs stranded on, 97.
----, geysers of, 246, 553, 555.

Iceland, volcanic eruptions in, 424.
----, comparison between the lavas of Central France and, 426.
----, new island near, 425.
----, polar bear drifted to, 679.

Igneous action. _See_ Volcanic.

Igneous causes. _See_ Book II.
----, the antagonist power to action of running water, 198, 563, 711.

Ilford, tertiary strata at, 76.

Imbedding of organic remains. _See_ Fossilization.

India, buried cities in, 729, 731.
----, terrestrial mammalia of, 632.

Indo-pacific province of mollusca, 649.

Indus, delta of. recent changes in, 459, 769.
----, buried ships in, 758.

Infusoria in bog iron-ore, 722.
----, in volcanic rocks in Mexico, Peru, &c., 388.

Infusorial tuff, Pompeii, 388.

Inland cliffs, no proof of sudden elevation, 531.
----, seas, deltas of, 255.

Insects, geographical distribution of, 654.
----, certain types of, distinguish particular countries, 655.
----, their a