THE CRUST OF THE EARTH. 



deposition. 30. Stratified rocks of aqueous origin. 31. Circum- 

 stances corroborating this inference. 32. Stratified and unstratified 

 rocks. 33. Condition andjnaterials of transition rocks. 34. Animal 

 remains found in them. 35. No vegetable remains probable reason. 

 36. Fish and annelidans. 37. Stratified rocks in general. 38. 

 Secondary rocks. 39. Vast quantity of organic remains deposited in 

 them. 40. Tertiary rocks. 41. Diluvium, alluvium, and surface 

 soil. 42. Subdivision .of these principal groups of strata. 43. 

 General inference as to the condition and ages of stratified rocks. 

 44. They constitute a chronological scale. 45. Complexity and 

 defects of geological nomenclature. 



1 . IT cannot be matter of surprise that of all the great bodies of 

 the universe the earth, which has been assigned by the Creator as 

 the habitation of the human race, has received the largest share 

 of attention on the part of those who have devoted their faculties 

 to the observation and investigation of nature. Regarded in 

 different points of view it has formed the exclusive subject of 

 several branches of science. 



2. Taken in its entire mass, and considered in relation to the 

 other bodies of the solar system, it constitutes the subject of 

 MATHEMATICAL GEOGRAPHY, which includes the solution of such 

 problems as the determination of the magnitude of the earth 

 its exact form its relation to the other bodies of the solar system 

 its annual motion round the sun which produces the apparent 

 movement of that luminary through the signs of the Zodiac its 

 diurnal rotation which produces those apparent motions of the 

 firmament which cause the vicissitudes of day and night the 

 peculiar position of its axis which produces the succession of 

 seasons the division of the globe into zones and climates, and 

 the system of imaginary circles of latitude and longitude which 

 supply the means of expressing the position of all places on the 

 globe, relatively to each other, and to the equator and poles. 



3. The earth, viewed in regard to the various physical states of 

 its surface, constitutes the subject of PHYSICAL GEOGEAPHY, 

 which includes a description of the distribution of land and 

 water the extent and configuration of continents and islands 

 the elevation and prevailing direction of mountain chains the 

 form, extent, and direction of plains and valleys the general 

 altitude of the surface of the land above the common level of the 

 sea the effects of soil and climate, and the local distribution of 

 animal and vegetable productions. 



4. This division of geographical science also includes the 

 various phenomena of the ocean and seas, their depth, salt- 

 ness, and temperature, the prevailing direction and velocity of 

 ocean currents, the extent of the polar ice and circumstances 

 incidental to it. 



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