OCR Text |
Show X CONTENTS. CHAPTER IV. EVOLUTION AS THE KEY Tl.) DISTRU3UTION. Importance of the Doctrine of Evolution-The Origin of New Species-Variation in A~imals-The amount of variation in North American Birds-How new species anse from a variable species-Definition and Origin of Genera- Cause of the exti~ction of Species-The rise and decay of Species and Genera-Discontinuous specific areas, why rare-Discontinuity of the area of Parus palustris- Discontinuity of E~beriz~ s7hceniclus-The European and Japanese Jays- Supposed examples of discontmmty among North American Birds-Distribution and antiqu't o f F amiT I es-D'I scon t'm ui' ty a proof of antil}uity-Concluding Remarks I Y Pages 54- 69 CHAPTER V. THE POWERS OF DISPERSAT- OF ANIMALS AND PLANTS. Statement of the general question of Dispersal-The Ocean as a barrier to the disp~ rsal of Mammals-The dispersal of Birds"T"The dispersal of Reptiles- The drspersal of Insects-~he dispersal of Land Mollusca-Great antiquity of Landshells-:- Causes fa:~unng the abundance of Land-shells-The dispersal of Plants -SpeCial adaptabihty of Seeds for dispersal-Birds as agents in the dispersal of See~s-Oce~n c~rrents as agents in Plant dispersal-Dispersal along mountainchams- Antiquity of Plants as affecting their distribution . p ages 70 - 80 CHAPTER VI. GEOGRAPHICAL AND GEOLOGICAL CHANGES: TilE PERJI!ANENCE OF CONTINENTS. Ch:~!~:~~ Land and Sea, their ~ature and extent-Shore-deposits and stratified of Chall heFMo~ements of Contments-Supposed oceanic formations. the Origin t ~- <r~s -water and Shore-deposits as proving the permanen~e of Continen s- ceanrc Islan~~ as indications of the permanence of Continents and Ocea~s-General stabthty of Continents with constant change of form-Eft' t f ~;~:~u:n~~l ~ha~ges 1 on t~ Distribution of Animals-Changed distribution p:~v:cl x me amm~ s o different epochs-Summary of evidence for the general permanence of Contments and Oceans . Pages 81- 102 CHAPTER VII. CHANGES OF CLIMATE WHIC H HA V.E INFLUENCED THE DISPERSAL OF ORGANISMS : THE GLACIAL EPOCli. Proofs of the recent occurrence of a Glacial E . Glacial deposits of Scotland. the "T'll" I ~och-Morames-Travelled Blocks-of Scotland-Glacial pheno~ena of ~or~ l ere~ces from the glacial p~enomena on animal life-Warm and cold . . meriCa-E~ects o~ the GlaCial Epoch cold and warm periods-Evidence pe;t?ds- Pal:eontologiCal evtdence of alternate and in North America-Mi ration o mtergl~cia~ warm periods on the Continent Glacial Epoch g s and extmctwns of Organisms caused by the . Pages 103- 120 CONTENTS. x:i CHAPTER VIII. THE CAUSES OF GLACIAL EPOCHS. Various suggested causes-Astronomical causes of changes of Climate- Difference of Temperature caused by varying distances of the Sun-Properties of air and water, snow and ice, in relation to Climate-Effects of snow on Climate-High land and great moisture essential to the initiation of a Glacial Epoch-Perpetual snow nowhere exists on lowlands-Conditions determining the presence or absence of perpetual Snow-Efficiency of Astronomical causes in producing Glaciation- Action of meteorological causes in intensifying Glaciation-Summary of causes of Glaciation-Effect of clouds and fog in cutting off the Sun's beatSouth Temperate America as illustrating the influence of Astronomical causes on Climate-Geographical changes how far a cause of Glaciation-Land acting as a barrier to ocean-currents-The theory of interglacial periods ancl their probable character-Probable effect of winter in aphelion on the climate of Britain-The essential principle of climatal change restated-Probable date of the last Glacial Epoch-Changes of the sea-level dependent on Glaciation-The planet Mars as bearing on the theory of excentricity as a cause of Glacial Epochs Pages 121-162 CHAPTER IX. ANCIENT GT.ACIAL EPOCHS, AND MILD CLIMATES IN THE ARCTIC REGIONS. Mr. Croll's views on ancient Glacial Epochs-Effects of Denudation in destroying the evidence of remote Glacial Epochs-Rise of sea-level connected with Glacial Epochs a cause of further denudation-'What evidence of early Glacial Epochs may be , expected-Evidences of Ice-action during the Tertiary Period-The weight of the negative evidence-Temperate climates in the Arctic RegionsThe Miocene Arctic flora-Mild Arctic climates of the Cretacious Period- Stratigraphical evidence of long-continued mild Arctic conditions---:The causes of mild Arctic climates-Geographical conditions favouring mild northern climates in Tertiary times---The Indian Ocean as a source of heat in Tertiary times-Conclition of North America during the Tertiary Period-Effect of high excentricity on warm Polar climates-Evidences as to climate in the Secondary and Palreozoic Epochs-Warm Arctic climates in early Secondary and Palreozoic times-Conclusions as to the climates of Secondary and Tertiary Periods-General view of Geological Climates as dependent on the physical features of the Earth's surface -Estimate of the comparative effects of geographical and physical causes in producing changes of climate . Pages 163-202 CHAPTER X. THE EARTli'S AGE, AND THE. RATE OF DEVELOPMENT OF ANlHA.I,S AND PLANTS. Various estimates of Geological Time-Denudation and deposition of Strata as a measure of Time-How to estimate the thickness of the Sedimentary RocksHow to estimate tho average rate of deposition of the Sedimentary Rocks- The rate of Geological change probably greater in very remote times-Value of the preceding estimate of Geological Time-Organic modification dependent on Change of Conditions-Geographical mutations as a motive power in bringing about Organic Changes-Climatal revolutions as an agent in producing Organic Changes-Present condition of the Earth one of exceptional stability as regards Climate-Date of last Glacial Epoch and its bearing on the Measurement of Geological time-Qonchlding Remarks . Pages 203-229 |