ARCTIC CLIMATE. ' 61 



ingenious hypothesis. He first states that the amount of 

 heat derived by the earth from the sun increases or dimi- 

 nishes with the eccentricity of the earth's orbit ; and that 

 this eccentricity is known to be slowly decreasing. He next 

 shows that the actual eccentricity of many of the planets 

 is known to be very considerable indeed ; and concludes 

 that we have only to form the very natural conception, that 

 this eccentricity of the earth's orbit was formerly greater 

 than it pow is equal to that of several of the planets, to 

 arrive at the conclusion that the slow diminution of such 

 eccentricity may have produced a refrigeration of climate 

 equal to that indicated by the geological phenomena just 

 described. 



Whatever may be the cause, the fact is indisputable ; the 

 tropical climate of the primeval earth is demonstrated by the 

 character of its productions ; and we are compelled to admit 

 that a cause then prevailed, or, possibly, a combination of the 

 causes above enumerated, which was sufficient to overcome 

 the effect of the diurnal and annual motion of the globe, and 

 to render its surface a vast hothouse, calculated for the 

 growth of ultra-tropic forms of animal and vegetable life ; 

 while the circumstance is one which the student must regard, 

 not merely as an abstract truth, but as a principle fraught 

 with the most useful and instructive application. No lesson 

 in science is more difficult than that which teaches us to 

 dismiss impressions which early associations have rendered 

 familiar, and to substitute opinions which, though more 

 correct, are strange and new. In investigating the ancient 

 history of the earth, we must change land to sea, and sea to 

 land; we must transport ourselves to distant regions, and 

 to torrid climes ; we must regard its oceans as vyeing in 

 extent and grandeur with the Atlantic or Pacific, abounding 

 in coral reefs and islands, and with tropic forms of marine 

 life ; its lakes as inland seas ; its rivers such as to rival the 

 Amazon or Mississippi ; its forests groves of ferns, canes, 

 palms, bananas, and bamboos ; its plains luxuriant savannahs, 

 overgrown with grasses and gigantic reeds, which sheltered 

 and supported gigantic reptiles ; the whole scene must 

 present the panorama of a torrid clime, with its colossal 

 . forms of animal and vegetable existence. 



ARCTIC CLIMATE. From various phenomena which have 



