PHYSICAL GEOGRAPHY. 301 



has been found that a perceptible sinking resulting from a 

 disturbance of the strata of the upper surface sometimes 

 occurs, corresponding with an elevation elsewhere, as, for 

 instance, in West Greenland, according to Pingel and Graah, 

 in Dalmatia and in Scania. 



Since it is highly probable that the oscillatory movements of 

 the soil, and the rising and sinking of the upper surface, were 

 more strongly marked in the early periods of our planet than 

 at present, we shall be less surprised to find in the interior of 

 continents some few portions of the Earth's surface lying 

 below the general level of existing seas. Instances of this 

 kind occur in the soda lakes described by General Andreossy, 

 the small bitter lakes in the narrow Isthmus of Suez, the 

 Caspian Sea, the Sea of Tiberias, and especially the Dead 

 Sea.* The level of the water in the two last named seas, is 

 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,f as do a l >so tne observations of Darwin on the coral 



* Humboldt, Asie centrale, t. ii. pp. 319-324; t. iii. pp. 549-551. 

 The depression of the Dead Sea has been successively determined by the 

 barometrical measurements of Count Bertou, by the more careful ones of 

 Russegger, and by the trigonometrical survey of Lieut. Symond, of the 

 Royal Navy, who states that the difference of level between the surface 

 of the Dead Sea and the highest houses of Jaffa is about 1605 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 Capt. 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 Lieut. Symond (Jameson's Edinburgh New 

 Philosophical Journal, vol. xxxiv. 1843, p. 178,) gives 1312 feet as the 

 final result, of two very accordant trigonometrical operations. 



t Sur la Mobilite du fond de la Mer Caspienne, in my Asie centr. t 

 t. ii. pp. 283-294. The Imperial Academy of Sciences of St. Peters- 

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

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

 different places near Baku, in the peninsula of Abscheron. In the same 

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



