INTRODUCTION TO GEOLOGt 



CHAPTER L 



Objects of the Science denominated Geology. — The Shape and Density of the 

 Earth. — Opinions respecting the internal Parts of the Globe. — Centrarileat. — 

 Temperature of the Earth. — Sea and dry Land.—Proportion of the Earth's Sur- 

 face habitable by Man. — On the Appearances which led to the first Division of 

 Rocks into Primary and Secondary. — Classification of Ptocks. — Districts in 

 which the different Classes appear in England. — The present Islands and Con- 

 tinents formerly covered by the Ocean. — Existing Proofs of this in Great Brit- 

 ain and various Parts of the World. — Fossil Remains of marine Animals, Ve- 

 getables, and land Ctuadrupeds ; the Strata in which they are imbedded formed 

 in Succession at difierent Epochs. — On human Bones occasionally imbedded in 

 Rock. — Inferences respecting the former Condition of the Globe.—Remarkable 

 Passage in the Institutes of Menu. 



In this Chapter the author has endeavoured to give such an outline 

 of the science, and its practical application to the knowledge of the Ge- 

 ology of England, as may be clearly and easily understood by the gener- 

 al reader, and prepare him for the per usal of the succeeding Chapters,' 



There are perhaps few persons possessed of much curiosity iii 

 early life, to whom the following question has not frequently present- 

 ed itself — What is the world made of^ Now this question, with 

 certain conditions, comprises the most important objects of geologi- 

 cal research ; namely, What are the substances of which the Earth 

 is composed ? What is the order in ivhich they are arranged ? What 

 are the changes they appear to have undergone ? — ^But how are 

 satisfactory answers to these inquiries to he obtained ? 



When we examine the terrestrial globe, where the solid parts are 

 uncovered and exposed to our view, we observe vast masses of rock 

 or stone lying in apparent confusion on each other : or, should we 

 perceive some regularity in their position and arrangement, we soon 

 lose sight of it again by the intervention of other rocks. In this de- 

 partment of nature all seems vast, unshapen, and chaotic; but let 

 us not be discouraged, for we may recollect that the grandest objects 

 in the material universe, seldom present to the hasty view of the su- 

 perficial observer, immediate proofs of order or design. 



The shepherd who first discovered that the planets were not fixed 

 in the heavens, and noticed their apparently intricate wanderings 

 among the stars, could not possibly anticipate the regularity and har- 

 monious simplicity of their movements, which subsequent observations 

 have demonstrated, 



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