PHYSICAL GEOGRAPHY. 297 



666 and 1312 feet below the level of the Mediterranean. If 

 we could suddenly remove the alluvial soil which covers the 

 rocky strata in many parts of the earth's surface, we should 

 discover how great a portion of the rocky crust of the earth 

 was then below the present level of the sea. The periodic, 

 although irregularly alternating rise and fall of the water of 

 the Caspian Sea, of which I have myself observed evident 

 traces in the northern portions of its basin, appears to prove, ^ 

 as do also the observations of Darwin on the coral seas,t that 

 without earthquakes, properly so called, the surface of the 

 earth is capable of the same gentle and progressive oscilla- 

 tions as those which must have prevailed so generally in the 

 earliest ages, when the surface of the hardening crust of the 

 earth was less compact than at present. 

 • The phenomena to which we would here direct attention 

 remind us of the instability of the present order of things, and 

 of the changes to which the outlines and configuration of con- 

 tinents are probably still subject at long intervals of time. 

 That which may scarcely be perceptible in one generation, 

 accumulates during periods of time, whose duration is revealed 

 to us by the movement of remote heavenly bodies. The east- 

 ern coast of the Scandinavian peninsula has probably risen 



tween the surface of the Dead Sea and the highest houses of Jaffa is 

 about 160.5 feet. Mr. Alderson, who communicated this result to the 

 Geographical Society of London in a letter, of the contents of which I 

 was informed by my friend, Captain Washington, was of opinion (Nov. 

 28, 1841) that the Dead Sea lay about 1400 feet under the level of the 

 Mediterranean. A more recent communication of Lieutenant Symond 

 (Jameson's Edinburgh New Philosophical Journal, vol. xxxiv., 1843, p, 

 178) gives 1312 feet as the final result of two very accordant trigono- 

 metrical operations. 



* Sur la Mobility du fond de la Mer Caspienne, in my Asie Centr., t, 

 ii., p. 283-294. The Imperial Academy of Sciences of St. Petersburgh. 

 in 1830, at my request, charged the learned physicist Lenz to place 

 marks indicating the mean level of the sea, for definite epochs, in dif- 

 fei'ent places near Baku, in the peninsula of Abscheron. In the same 

 manner, in an appendix to the instructions given to Captain (now Sir 

 James C.) Ross for his Antarctic expedition, I m*ged the necessity of 

 causing marks to be cut in the rocks of the southern hemisphere, as 

 had already been done in Sweden and on the shores of the Caspian 

 Sea. Had this measure been adopted in the early voyages of Bougain- 

 ville and Cook, we should now know whether the secular relative 

 changes in the level of the seas and land are to be considered as a gen- 

 eral, or merely a local natural phenomenon, and whether a law of di 

 rection can be recognized in the points which have simultaneous ele- 

 vation or depression. 



t On the elevation and depression of the bottom of the South Sea, 

 and the different areas of alternate movements, see Darwin's Journal, 

 p. 557, 5G 1-566. 



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