167.

Tidal action,
recent studies of, 131, 132;
marshes of North America, 340.

Tides,
carving channels, 129;
effecting the earth's rotation, 130;
effect of, on marine life, 130;
height of, 128, 129;
moon and sun, 126, 127;
normal run of the, 127;
production of, 131;
of the trade winds, 150;
solar, 127;
travelling of, 127, 128.

Tillage introducing air into the pores of the soil, 331.

Tornadoes, 112, 113, 317;
development of, 113;
effect of, on buildings, 113;
fiercest in North America, 113;
length of, 115;
resemblance of, to hurricanes, 115;
upsucking action of, 114, 115.

Torrents, 177-179, 204.

Trade winds. See under WINDS.

Training in language,
diminishing visual memory, 401;
soldiers to measure distances, 28;
to measure intervals of time, 28;
for a naturalist, 25-29.

Tunnels, natural, 257.

Uranus, 70.

Valley of Val del Bove formed from disturbances of Mount AEtna, 294.

Valleys,
diversity in the form of river, 188-191;
river, 193.

Vapour, 156, 157, 159, 163;
gravitative attraction of, 34, 35;
nebular theory of, 52, 53;
original, of the solar system, 52, 53.

Vegetation,
and dew, 160;
in a measure, independent of rain, 160;
protecting the soil, 316, 317.

Vein, diagram of a, 260.

Venus, 64, 78;
recent observations of, by Mr. Percival Lowell, 64.

Vesuvian system, study of the, 285.

Vesuvius. See MOUNT VESUVIUS.

Visualizing memories, 402, 403.

Volcanic action, 268-276.

Volcanic eruption of A.D. 79, 288;
important facts concerning, 276-279;
islands, 272;
lava a primary feature in, 266;
observations of, made from a balloon, 301;
peaks along the floor of the sea, 272, 273;
possibility of throwing matter beyond control of gravitative
energy, 300.

Volcanoes, 125, 203, 263;
abounding on the sea floor, 302;
accidents from eruptions of, 288;
along the Pacific coast, 271;
ash showers of, maintaining fertility of the soil, 289;
distribution of, 271;
eruption of, 286-294, 368;
explosions from, coming from a supposed liquid interior
of the earth, 275;
exporting earth material, 310;