306 COSMOS. 



nature can on\y give a maximum limit, that the centre of 

 gravity of the volume of the land raised above the present 

 level of the sea in Europe and North America, is respectively 

 situated at an elevation of 671 and 748 feet, while it is at 1 132 

 and 1152 feet in Asia and South America. These numbers 

 show the low level of northern regions. In Asia the vast 

 Steppes of Siberia are compensated for by the great elevations 

 of the land (between the Himalaya, the North Thibetian 

 chain of Kouen-lun, and the Celestial Mountains), from 

 28 30' to 40 north latitude. We may to a certain extent 

 trace in these numbers the portions of the earth, in which the 

 plutonic forces were most intensely manifested in the interior, 

 by the upheaval of continental masses. 



There are no reasons why these plutonic forces may not in 

 future ages add new mountain- systems to those which Elie de 

 Beaumont has shown to be of such different ages, and inclined 

 in such different directions. Why should the crust of the 

 earth have lost its property of being elevated in ridges? 

 The recently elevated mountain-systems of the Alps and the 

 Cordilleras exhibit in Mont Blanc and Monte Rosa, in Sorata, 

 Illimani, and Chimborazo, colossal elevations which do not 

 favour the assumption of a decrease in the intensity of the 

 subterranean forces. All geognostic phenomena indicate the 

 periodic alternation of activity and repose ; * but the quiet we 

 now enjoy is only apparent. The tremblings which still 

 Agitate the surface under aU latitudes, and in every species of 

 rock, the elevation of Sweden, the appearance of new islands 

 of eruption, are all conclusive as to the unquiet condition 01 

 our planet. 



The two envelopes of the solid surface of our planet the 

 liquid and the aeriform, exhibit, owing t- A the mobility of 



the mean height of continents, at 3280 feet, is at Jsast three times too 

 high. The immortal author of the Mecanique celeste (t. v. p. 14), 

 was led to this conclusion by hypothetical views as to the mean depth 

 of the sea. I have shown (Asie centr., t. i. p. 93,) that the old Alex- 

 andrian mathematicians, on the testimony of Plutarch (in JEmilio 

 Paulo, cap. 15), believed tliis depth to depend on the height of the 

 mountains. The height of the centre of gravity of the volume of the 

 continental masses is probably subject to slight variations in the course 

 of many centuries. 



* Ziceiter geoiOffiscker Brief von Elie de Beaumont an Alexander 

 tiu (Ivmboldt, in Poggendorff's Annalen, bd. xxv. s. 1- -58. 



