GEOLOGY. 293 



turning-point in its history the earth gives a sudden whirl, and assumes 

 a new position. We must first endeavor to imagine what would be the 

 effect upon the strata composing the crust of the earth consequent upon the 

 movement of the protuberant equatorial mass; the strata would be thrown 

 into undulations in quasi-loxodromic lines, sueh as have been described by 

 Humboldt and others. 



And what we must next inquire would be the effect upon the great volume 

 of water in the seas in which the strata were being deposited. The water 

 would be thrown with irresistible violence upon the continents, whole races 

 of animals and plants would be simultaneously destroyed, and the surface 

 of the earth ground down by the water itself, and the forcing along of vast 

 masses of detrital matter over it; and finally there would be such a change, 

 be it small or great, in the position of the poles of the earth, and in the incli- 

 nation of its axis, as would produce a change of climate in every part of the 

 world, but more marked in the arctic and temperate regions than the tropi- 

 cal. We have but to suppose this repeated again and again to account for 

 all the observed phenomena. 



In weighing the probability of the truth of this theory, we must take 

 into consideration the fact, that no other theory has been before advanced 

 which would account for these so intimately correlated phenomena being 

 produced by one and the same cause; and I still hope that some at least 

 of my scientific friends will admit that I have given them in it a valuable 

 "wrinkle." 



In opposition to these vio^vs of Sir Henry James, Mr. Jukes, one of the 

 directors of the Geological Survey of Great Britain, publishes the following 

 communication in the Athenceum, under date of September 3d, 1860. He 

 says : 



In the first place, I would object that there is no proof that " there has 

 been everywhere a change of climate;" since the tropical and sub-tropical 

 portions of the earth's surface may have always had pretty much the same 

 mean temperature which they have now, for everything we can show to the 

 contrary. It is, indeed, almost certain that the arctic and northern temperate 

 regions wei'e once warmer than they are now, and that warmer climate seems 

 to have endured for all geological time until a very recent geological period. 

 It is equally certain that large parts at least, if not the whole (there is some 

 doubt as to that), of the northern temperate regions were, during that 

 recent geological period, considerably colder than they are now. This colder 

 climate seems, during that same period, to have prevailed as far south as 

 Northern India, judging from the former greater extension of the glaciers of 

 the Himalaya, as described by Dr. Hooker and others, though possibly that 

 might admit of explanation on the supposition of greater moisture there, 

 caused by the Bay of Bengal extending up the present valley of the Ganges. 

 We have, however, no reason to look to any other spot on the globe than the 

 present north pole as the centre of that cold climate during this glacial or 

 pleistocene period. Neither has any one yet ventured to point to any other 

 region of the globe as having been possibly its arctic region during any 

 previous geological period, basing his argument on the fossils of that 

 region having a more arctic character than the contemporaneous fossils of 

 surrounding countries. 



The change of climate seems, as far as we can judge, to have been a gen- 

 eral change from an " insular " to a " continental " climate, or, in other words, 

 a change from one where a milder temperature was more widely diffused over 



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