SECT, x.] AXIS OF ROTATION INVARIABLE. 85 



ocean by a scratch on its surface. Consequently the gradual 

 elevation of a continent or chain of mountains above the 

 surface of the ocean, or their depression below it, is no very 

 great event compared with the magnitude of the earth, and 

 the energy of its subterranean fires, if the same periods of 

 time be admitted in the progress of geological as in astro- 

 nomical phenomena, which the successive and various races 

 of extinct beings show to have been immense. Climate is 

 always more intense in the interior of continents than in 

 islands or sea-coasts. An increase of land within the tropics 

 would therefore augment the general heat, and an increase 

 in the temperate and frigid zones would render the cold 

 more severe. Now it appears that most of the European, 

 North Asiatic, and North American continents and islands 

 were raised from the deep after the coal-measures were 

 formed in which the fossil tropical plants are found ; and a 

 variety of geological facts indicate the existence of an 

 ancient and extensive archipelago throughout the greater 

 part of the northern hemisphere. Mr. Lyell is therefore of 

 opinion that the climate of these islands must have been 

 sufficiently mild, in consequence of the surrounding ocean, to 

 clothe them with tropical plants, and render them a fit abode 

 for the huge animals whose fossil remains are so often 

 found; that the arborescent ferns and the palms of these 

 regions, carried by streams to the bottom of the ocean, were 

 imbedded in the strata which were by degrees heaved up by 

 the subterranean fires during a long succession of ages, till 

 the greater part of the northern hemisphere became dry 

 land as it now is, and that the consequence has been a con- 

 tinual decrease of temperature. 



It is evident, from the marine shells found on the tops of 

 the highest mountains and in almost every part of the globe, 

 that immense continents have been elevated above the ocean 

 which must have engulfed others. Such a catastrophe would 

 be occasioned by a variation in the position of the axis of 

 rotation on the surface of the earth ; for the seas tending 



