288 PHYSICAL GEOGRAPHY. 



where; this has been observed in West Greenland (by 

 Pingel and Graah), in Scania, and in Dalmatia. 



As it appears more than probable that, in the earlier 

 periods of our planet, the elevations and depressions of its 

 surface were much more considerable than at present, we 

 ought not to be surprised at finding, even in the interior of 

 continents, portions of the surface depressed below the 

 general level of the present sea ; as the small natron lakes 

 described by General Andreossy, the small bitter lakes of 

 the isthmus of Suez, the Caspian Sea, the lake or sea of Tibe- 

 rias, and above all, the Dead Sea. ( 353 ) The levels of the 

 two last-named seas are respectively 625 (666 English) and 

 1230 (1311 English) feet below the level of the Mediter- 

 ranean. If we could remove the alluvial soil which so fre- 

 quently covers the rocky strata in the level portions of the sur- 

 face of the earth, we should discover how many parts of the 

 denuded crust are below the present level of the sea. The 

 periodical, but irregularly recurring, rise and fall of the 

 Caspian, of which I observed distinctly marked traces in the 

 northern portion of the basin of that sea, ( 354 ) and the obser- 

 vations of Darwin in the Coral Sea, ( 35S ) appear to indicate 

 that, without earthquakes properly so called, the surface of the 

 earth still undergoes in some places slow and continued 

 oscillations, similar to those which, in earlier times, must 

 have been of very general oocurrence in the then thinner 

 solid crust. 



The phenomena to which we are now directing our atten- 

 tion remind us of the instability of the present order of 

 things, of the changes to which the outline and form of 

 continents are probably still subject in long intervals of 

 time. These variations, though hardly sensible from one 



