PHYSICAL GEOGRAPHY. 299 



oarometer alone can not afford a certain evidence of the gen- 

 sral change of level in the ocean. The remarkable fact that 

 some of the ports in the Mediterranean were repeatedly left 

 dry during several hours at the beginning of this century, ap- 

 pears to show that currents may, by changes occurring in 

 their direction and force, occasion a local retreat of the sea, 

 and a permanent drying of a small portion of the shore, with- 

 out being followed by any actual diminution of water,%or any 

 permanent depression of the ocean. We must, however, be 

 very cautious in applying the knowledge which we have late- 

 ly arrived at, regarding these involved phenomena, since we 

 might otherwise be led to ascribe to water, as the elder ele- 

 ment, what ought to be referred to the two other elements, 

 earth and air. 



As the external configuration of continents, which we have 

 already described in their horizontal expansion, exercises, by 

 their variously-indented littoral outlines, a favorable influence 

 on climate, trade, and the progress of civilization, so likewise 

 does their internal articulation, or the vertical elevation of 

 the soil (chains of mountains and elevated plateaux), give rise 

 to equally important results. Whatever produces a poly- 

 morphic diversity of forms on the surface of our planetary 

 habitation — such as mountains, lakes, grassy savannas, or 

 even deserts encircled by a band of forests — impresses some 

 peculiar character on the social condition of the inhabitants. 

 Ridges of high land covered by snow impede intercourse ; but 

 a blending of low, discontinued mountain chains* and tracts 

 of valleys, as we see so happily presented in the west and 

 south of Europe, tends to the multiplication of meteorological 

 processes and the products of vegetation, and, from the variety 

 manifested in different kinds of cultivation in eadh district, 

 even under the same degree of latitude, gives rise to wants 

 that stimulate the activity of the inhabitants. Thus the aw- 

 ful revolutions, during which, by the action of the interior on 

 the crust of the earth, great mountain chains have been ele- 

 vated by the sudden upheaval of a portion of the oxydized 

 exterior of our planet, have served, after the establishment 

 of repose, and on the revival of organic life, to furnish a rich- 

 er and more beautiful variety of individual forms, and in a 

 great measure to remove from the earth that aspect of dreary 



* Humboldt, Rel. Hist., t. iii., p. 232-234. See, also, the able re- 

 marks on the configuration of the earth, and the position of its lines 

 of elevation, in Albrechts von Roon, Grundzugen der Erd Volkei- und 

 etaatenkunde, Abth. i., 1837, s. 158, 270, 276. 



