Geology
the science which investigates the bygone history of the earth with the view of accounting for its present condition. It is the province of physical and political geography to de- GEOLOGY scribe what the earth now is, geology attempts to furnish the reason why.
History. Though it was only during the 19th century that geology has started up into the vigor of manhood, yet its birth took place ages ago. Isolated geological observations or hypotheses occur abundantly in ancient literature. "As Huttonian hypothesis. Egypt, according and under it is turned up as it were fire" to Herodotus, is the gift of the Nile, that is, the river brought down the silt which to Herodotus, is the gift of the Nile, that and other parts of Lower Egypt. The constitutes the fertile soil of the delta and other parts of Lower Egypt. The best geologist of antiquity was the gewith Werner, who was a professor in the century A. D. Modern geology began century A. D. with Werner, who was a professor in the Modern geology began universal formations had been deposited in 1775. He believed that a series of universal formations had been deposited in succession from a chaotic fluid. Basalt was supposed to have had the same origin, but to this view various contipublished in 1788 his "Theory of the Earth," developed in a separate work in 1795. He assumed no causes but those now existing. He showed that geology economy of the world," he said, "he could find no trace of a beginning, no prospect of an end." He held basalt, granite, etc., to be of igneous origin were called Neptunists, their opponents gin . The Wernerians his "Fossil Bones," which gave a great impulse to palæontology.
Forces or Causes in Operation. After inquirers had outgrown the belief in fossils produced by the plastic power of nature or all entombed simultaneously by the Noachian deluge, the belief was entertained that there had been a series causing the universal destruction of all pre-existing species. The belief was also causing the universal destruction of all entertained that some external causes, say the forces producing earthquake and volcanic action, were more potent in say the forces producing earthquake and former times than now. This Professor defines to be any form of geological speculation which, in order to account for these phenomena, supposes the operation of forces different in their nature tion of forces different in their nature those which are at present in action in the universe.
The second school of geology is that called by Huxley uniformitarianism.
This looks only to causes now in operation for the explanation of geological This looks only to causes now in opera- 1. the founder, though it was Sir Charles GEOLOGY Lyell that carried it forward to triumph. the causes now in operation are still producing, and that nearly every phenom- He showed the enormous changes which causes acting suddenly and briefly, could than those in action now, but operating causes acting suddenly and briefly, could through immense periods of bygone time. be produced by causes not more intense In his "Principles of Geology," he exwater acting in connection with tides, amines aqueous causes, the action of water acting in connection with tides, currents, etc., in seas, rivers, and lakes, also the action of ice in all its forms.
Next he inquires into igneous causes, volcanoes, and earthquakes. Climate and organic life are also carefully investigated in the work. geologists is called by Professor Huxley evolutionism; it accepts nearly the whole The doctrine of the third school of of uniformitarianism, except the part referring to the development of organic life. In his later years Sir Charles Lyell referring to the development of organic became an evolutionist. See DARWINIAN THEORY: EVOLUTION. itarian and the evolutionist believe that they may draw to any extent on what Geologic Time. Both the uniformmay be called the bank of time, which quantity of hypothetical paper." Sir may be called the bank of time, which William Thompson holds that any such drafts must be limited "within some such period as 100,000,000 years"; and the time at call only about 60,000,000 another natural philosopher considers years. Huxley believes the necessity for these limitations is not proved, though lions of years might be enough to account for geological phenomena. perhaps one, two, or three hundred milcount for geological phenomena. command, the sedimentary strata ha lions of years might be enough to acbeen laid down by water, the relative thickness of each stratum will measure been laid down by water, the relative ha having for its deposition. ord is made up as follows, beginning with the five great thickness of each stratum will measure PERIODS.
5. Quaternary. The age of man. 4. Cenozoic Period. Age of Mammals.
5. Quaternary. The age of man. PERIODS. 3. Mesozoic Period. Age of Reptiles. 4. Cenozoic Period. Age of Mammals. dawn of life.
1. Archæan Period.
Age of Coal Plants.
Age of Fishes.
Age of Inver- Age of Coal Plants. gether with their dependent series and sub-divisions in descending order:
The following list gives the eras to- GEOLOGY ERAS AND SERIES. 9. Quaternary or Post Tertiary: (3) Recent, (2) Champlain, (1) Glacial. 8. Tertiary Era: (4) Pliocene, (3) Miocene, (2) Oligocene, (1) Eocene. 7. Cretaceous Era: (4) Laramie, (3) Colorado, (2) Dakota, (1) Lower. 6. Jura-Trias: (b) Jurassic; (3) Purbeck, (2) Oölite, (1) Lias, (a) Triassic: (4) Rhætic, (3) Upper, (2) Middle, (1) Lower. 5. Carboniferous Era: (3) Permian, (2) Carboniferous, (1) Sub-carboniferous. 4. Devonian Era: (5) Catskill and Chemung, (4) Portage, (3) Hamilton, (2) Corniferous, (1) Oriskany. 3. Upper Silurian:. (3) Lower Helderberg, (2) Onondaga, (1) Niagara. 2. Lower Silurian: (3) Trenton, (2) Chazy, (1) Calciferous. 1. Cambrian.
Eozoic (dawn of life), Azoic (lifeless).
SUB-DIVISIONS.
GEOMETRY