little water, 375;
Italian, considered collectively, 296, 297;
Neapolitan eruptions of and the history of civilization, 288;
subsidence of the earth after eruption of, 287, 291;
origin of, 263-274;
phenomena of, 263-267;
submarine, 301;
travelling of ejections from, 287, 288.

Waters,
crevice, 250;
of the earth, 250, 251;
cutting action of, 117, 192;
drift, from the poles, 151;
journey of, from the Arctic Circle to the tropics, 151, 152;
dynamic value of, 171;
expansion of, in rocks, 270;
geological work of, 168-206;
in air, 99;
of the clouds usually frozen, 207;
pure, no power for cutting rocks, 204;
rock, 250, 263;
sea, minerals in, 185;
store of the earth, 125;
system of, 125, 156;
tropical, 151;
velocity of the, under the equator, 150;
wearing away rocks, 178, 179;
underground, carrying mineral matter to the sea, 193;
chemical changes of, leading to changes in rock material, 262, 263;
effect of carbonic-acid gas on, 251;
operations of the, 126;
wearing away rocks, 178, 179;
work of, 250.

Waterfalls, 189-193;
cause of, 191;
the Yosemite, 192;
Niagara, 191, 192;
numerous in the torrent district of rivers, 192;
produced by dikes, 192;
valuable to manufactures, 192, 193.

Waterspouts, 115, 116;
atmospheric cause of, 116;
firing at, 116;
life of a, 116;
picturesqueness of, 116;
the water of fresh, 117.

Waves, 128, 129, 132, 145;
action of friction on, 135, 136;
break of the, 136;
endurance of sand against the, 145;
force of, 133, 136, 139;
marine, caused by earthquakes, 387;
of earthquakes, 389;
peculiar features in the action of, 137;
size of, 137, 138;
stroke of the, 144;
surf, 135;
tidal height of, 132;
undulations of, 132;
wind, 132;
wind influence of, on the sea, 134, 135;
wind-made, 128.

Ways and means of studying Nature, 9.

Weeds of the sea, 155.

Well, artesian, 258, 259.

Whirling of fluids and gas, 36, 37.

Whirlwinds in Sahara, 121.

Will-o'-the-wisp, 167.

Winds, 101, 110, 122, 317;
effect of sand, 122;
hurricane, 110;
illustration of how they are produced,