744 THE WONDERS OF GEOLOGY. Lect. VII. 



which it must be admitted is highly ingenious, has been proposed by 

 an American philosopher.* This author, from a comprehensive view 

 of the phenomena which modern geological researches have brought 

 to light, contends that the following general principles may be 

 established: — 



" 1st. That, notwithstanding the displacements the strata have un- 

 dergone from subterranean movements, and the destructive 

 effects of deluges and alluvial action, during the lapse of innu- 

 merable ages, there remains unquestionable evidence of a great 

 uniform zone of tropical climate, which favoured the existence 

 of vegetable and animal productions of the land and ocean, 

 and formerly surrounded the globe, in a different course from 

 that of the present tropics : and that this is manifest in the 

 organic remains and oceanic deposits, wherever this region is 

 now elevated above the waters. 



2dly. That this tropical or torrid zone passed through nearly all 

 the present climates. 



3dly. That a uniformity of production has been found upon it in 

 numerous places. And, 



Lastly, That the changes on the earth's surface, which have pro- 

 duced the successive strata and organic remains, as far as these 

 are regular, are attributable to the progress of the perihelion 

 point around the ecliptic : and that by the precession of the 

 equinoxes, and the progress of the perihelion rotation of the 

 earth's orbit, the tropical zone, by very slow degrees, has 

 changed, and is still changing its position." 



Whether either or both of the above-named causes may 

 be regarde'd as applicable or adequate to have produced 

 any of the contemplated effects, I must leave to the astro- 

 nomers to determine: but there is another cause, which 

 was first suggested by Mr. Lyell, that possesses all the 

 essential requisites of a vera causa ; and that is, the varying 

 influence of the distribution of land and sea over the surface 

 of the earth ; and upon which, therefore, I would offer a 

 few comments. A change of such distribution in the lapse 

 of ages, by the degradation of the old continents, and the 



* An Essay on Organic llemains as connected with an ancient, 

 Tropical Region of the Earth. By Thomas Gilpin, Member of the 

 American Philosophical Society : Philadelphia, 1 8 I 



