234 



CAUSES OF VICISSITUDES IN CLIMATES. 



[Ch. XII. 



that the earth's axis had been for ages perpendicular to the 

 plane of the ecliptic, so that there was a perpetual equinox 

 and uniformity of seasons throughout the year ; that the 

 planet enjoyed this < paradisiacal ' state until the era of the 

 great flood ; but in that catastrophe, whether by the shock of 

 a comet, or some other convulsion, it lost its equipoise and 

 hence the obliquity of its axis, and with that the varied 

 seasons of the temperate zone, and the long nights and days 

 of the polar circles. 



When the progress of astronomical science had exploded 

 this theory, it was assumed, that the earth at its creation 

 was in a state of igneous fluidity, and that, ever since that 

 era, it had been cooling down, contracting its dimensions, and 



acquiring a solid crust. It was also taken for granted that 



this original crust was the same as that which we are now 

 studying, and which contains the monuments of a long series 

 of revolutions in the animate world. This notion, however 



pul 



e 



it referred the mind directly to the beginning of things, and 



from 



But the 



progress of geological investigation gradually dissipated the 

 idea, at first universally entertained, that the granite or 

 crystalline foundations of the earth's crust were of older date 

 than all the fossiliferous strata. It has now been demon- 

 strated that this opinion is so far from the truth that it is 



difficult 



more ancient than the olrlpsf. Vnnwn nv._ 



Such being the case, the question of original fluidity, although 



matter 



itimate 



with which the geologist is but little concerned. It may 

 relate to a state of things which preceded our earliest records 

 by a lapse of ages many times greater than the entire series 

 of geological epochs with which we are acquainted. 



If, instead of indulging in conjectures as to the state of the 

 planet at the era of its creation, we fix our thoughts steadily 

 on the connection at present existing between climate and 

 the distribution of land and sea, and then consider what 

 influence former fluctuations in the physical geography of the 

 globe must have had on superficial temperature, we may 



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