AGE OF THE GLOBE. 



48. To the question as to the lapse of time during which these 

 successive sedimentary strata have been formed, it is impossible 

 to give any answer even as definite as the estimates of their 

 thickness. All that can be said is, that the deposition from 

 turbid waters being generally a slow process, it may be imagined 

 that intervals of time of vast duration must have been required 

 for the formation of strata which measure many miles in 

 thickness. 



But besides the mechanical deposition of matters suspended in 

 water, we find numerous traces of chemical decomposition, which 

 could only have been effected in long intervals of time. Thus 

 deposits of limestone lie in frequent alternation with sandstones 

 and clays. These indicate a series of changes in the mode of 

 action, by which the total stratified mass was produced, consisting 

 of successive cessations and renewals in chemical and mechanical 

 action. 



In short all these effects combined with others, presently to be 

 mentioned, lead to the conclusion that the period during which 

 the human race and its contemporary tribes have existed upon 

 the earth, is but a brief interval compared with the immense 

 lapse of time occupied by the formation of the igneous rocks, by 

 the cooling down of the superficial part of the fused matter, and 

 the subsequent deposition of the stratified crust. 



49. It may be useful here briefly to recapitulate the history of 

 the globe, as we find it inscribed upon its crust. 



Originally a mass of fluid matter, in a state of igneous fusion, 

 it assumed the globular form in virtue of the mutual gravitation 

 of its parts. Launched by the Creator into space with a motion 

 of rotation round a certain diameter as an axis, it took the form 

 of an oblate-elliptical spheroid, flattened at the poles, in virtue of 

 the centrifugal force attending its rotation. The degree of 

 spheroidal ellipticity being of course precisely that which cor- 

 responded to its velocity of rotation. 



In this state its extremely exalted temperature would not only 

 maintain the matter at its surface in a state of fusion, but would 

 also keep a certain portion of the solid matter in a state of 

 sublimation, and all the liquid matter in a state of vapour sus- 

 pended in and mixed with the surrounding atmosphere. 



After a continuance of greater or less duration in this state, 

 the heat of the globe being continually radiated into the sur- 

 rounding space, the temperature of its surface would be gradually 

 diminished, and would, at length, fall below the point of fusion 

 of the matter composing its surface, and consequently the super- 

 ficial part would be solidified, and the globe would be coated, as 

 it were, by a thin skin or shell of solid matter, enclosing within 



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