Chapter XXII

Evaporation—Distribution of Vapour—Dew—Hoar-Frost—Fog—Region of Clouds—Forms of Clouds—Rain—Distribution of Rain—Quantity—Number of rainy Days in different Latitudes—Rainless Districts—Snow Crystals—Line of perpetual Snow—Limit of Winter Snow on the Plains—Sleet—Hail—Minuteness of the ultimate Particles of Matter— Their Densities and Forms—Their Action on Light—Colour of Bodies— Colour of the Atmosphere—Its Absorption and Reflection of Light— Mirage—Fog Images—Coronæ and Halos—The Rainbow—Iris in Dewdrops— The Polarization of the Atmosphere—Atmospheric Electricity—Its Variations—Electricity of Fogs and Rain—Inductive Action of the Earth—Lightning—Thunder—Distribution of Thunder-Storms—Back Stroke—St. Elmo’s Fire—Phosphorescence—Aurora—Magnetism— Terrestrial Magnetism—The Dip—Magnetic Poles and Equator—Magnetic Intensity—Dynamic Equator—Declination—Magnetic Meridian—Lines of equal Variation—Horary Variations—Line of Alternate Horary Phenomena—Magnetic Storms—Coincidence of the Lines of equal Magnetic Intensity with Mountain Chains—Diamagnetism 272

CHAPTER XXIII.

Vegetation—Nourishment and Growth of Plants—Effects of the different Rays of the Solar Spectrum—Classes—Botanical Districts 298

CHAPTER XXIV.

Vegetation of the Great Continent—Of the Arctic Islands—And of the Arctic and North Temperate Regions of Europe and Asia 312

CHAPTER XXV.

Flora of Tropical Asia—Of the Indian Archipelago, India, and Arabia 323

CHAPTER XXVI.

African Flora—Flora of Australia, New Zealand, Norfolk Island, and of Polynesia 330

CHAPTER XXVII.

American Vegetation—Flora of North, Central, and South America— Antarctic Flora—Origin and Distribution of the Cerealia—Ages of Trees—Marine Vegetation 341

CHAPTER XXVIII.

Distribution of Insects 363

CHAPTER XXIX.

Distribution of Marine Animals in general—Fishes—The Marine Mammalia—Phocæ, Dolphins, and Whales 368

CHAPTER XXX.

Distribution of Reptiles—Frogs and Toads—Snakes, Saurians, and Tortoises 383

CHAPTER XXXI.

Distribution of Birds in the Arctic Regions—In Europe, Asia, Africa, America, and the Antarctic Regions 392

CHAPTER XXXII.

Distribution of Mammalia throughout the Earth 412

CHAPTER XXXIII.

The Distribution, Condition, and future Prospects of the Human Race 436

APPENDIX.

Table of Heights above the Sea of some of the Principal Mountain Chains 475

GLOSSARY 487

INDEX 527

PHYSICAL GEOGRAPHY.