CHAPTER VI.

Carboniferous fauna continued—George Herbert's ode on "Man"—His idea of creation—What nature teaches on this subject—Molluscous animals—Range of species in time proportionate to their distribution in space—Two principles of renovation and decay exhibited alike in the physical world and the world of life—Their effects—The mollusca—Abundantly represented in the carboniferous rocks—Pteropods—Brachiopods—Productus—Its alliance with Spirifer—Spirifer—Terebratula—Lamellibranchs—Gastropods—Land-snail of Nova Scotia—Cephalopods—Structure of orthoceras—Habits of living nautilus,

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CHAPTER VII.

Classification of the naturalist not always correspondent with the order of nature—Incongruous grouping of animals in the invertebrate division—Rudimentary skeleton of the cephalopods—Introduction of the vertebrate type into creation—Ichthyolites of the carboniferous rocks—Their state of keeping—Classification of fossil fishes—Placoids—Ichthyodorulites—Ganoids—Their structure exemplified in the megalichthys and holoptychius—Cranium of megalichthys—Its armature of scales—Microscopic structure of a scale—Skeleton of megalichthys—History of the discovery of the holoptychius—Confounded with megalichthys—External ornament of holoptychius—Its jaws and teeth—Microscopic structure of the teeth—Paucity of terrestrial fauna in coal measures—Insect remains—Relics of reptiles—Concluding summary of the characters of the Carboniferous fauna—Results,

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CHAPTER VIII.

Sand and gravel of the boulder—What they suggested—Their consideration leads us among the more mechanical operations of Nature—An endless succession of mutations in the economy of the universe—Exhibited in plants In animals—In the action of winds and oceanic currents—Beautifully shown by the ceaseless passage of water from land to sea, and sea to land—This interchange not an isolated phenomenon—How aided in its effects by a universal process of decay going on wherever a land surface is exposed to the air—Complex mode of Nature's operations—Interlacing of different causes in the production of an apparently single and simple effect—Decay of rocks—Chemical changes—Underground and surface decomposition—Carbonated springs—The Spar Cave—Action of rain-water—Decay of granite—Scene in Skye—Trap-dykes—Weathered cliffs of sandstone—Of conglomerate—Of shale—Of limestone—Caverns of Raasay—Incident—Causes of this waste of calcareous rocks—Tombstones,

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CHAPTER IX.