and Orography of the Earth's Surface. 301 



alluvial period, at the same time that the central parts of 

 Europe and Africa were raised into the E.W. direction. In 

 Asia it would seem also that the great central elevation 

 of this continent preceded the end of the alluvial time, and 

 the direction of the eastern part of both Indian Peninsulas 

 was changed to N.S. 



The elevations and vault of the American meridian chains 

 were later events than the motions in the Old World ; but 

 these phenomena were similar, in as far as regards the trans- 

 verse crossing of the great E.W. subsidence of the Pacific. 



We ought not to forget that in every see-saw motion there 

 takes place a subsidence as well as an elevation, a principle 

 which is well exemplified in the plastic form of the earth's 

 surface. 



When the heights of central Europe, Africa, and Asia, with 

 some parts of the countries of the Mexican Gulf, were 

 raised during the alluvial period, in an equatorial direction, 

 some extensive parts of the low and flat countries of North- 

 ern Europe, Siberia, and even North America, were de- 

 pressed in the same direction, and this gave rise to the er- 

 ratic phenomena. Similar subsidences took place in that di- 

 rection in the south of Europe, Africa, and Asia, for instance 

 in the Mediterranean, the Gulf of Mexico, &c. 



On the contrary, when the meridian chains of North Ame- 

 rica were elevated, those of Eastern America were depressed, 

 especially in South America, where older islands disappeared 

 entirely under the Atlantic. Again the contrary took place : 

 — with the indications of elevation of the western coast of 

 America, we see a part of Greenland, and of Arctic America 

 subside. In the Old World the Siberian shores of the Icy 

 Sea, as well as the bosom of the Baltic and Scandinavia, were 

 elevated. All these see-saw-like motions took place in quite 

 contrary directions. In the recent Tertiary period, we find 

 some elevations in the meridian direction in the Old as well 

 as in the New World, but these were preceded by equatorial 

 subsidences. About the same time, facts shew, on the con- 

 trary, immense equatorial elevations in Central Europe and 

 Asia. Let us go back to the secondary periods, and we find 

 connected with Europe, Africa, Asia, and America, great 



