LAKES. 317 



interior of the continent, stretching northward to Orenberg on the Ural river, which is 

 500 versts, or about 335 miles, in a direct line from the shores of the Caspian. The 

 surface of the latter has been found, by levelling across the isthmus, to be about 81 feet 

 below that of the Black Sea. Humboldt considers the depression of this part of the 

 continent to have an intimate connexion with the upheaving of the Caucasian mountains, 

 of the elevated plain of Persia, and perhaps, more to the eastward, with the elevation of 

 the great mass of land which is designated by the vague and incorrect name of the 

 central plain of Asia. These are the more recondite speculations of geology, in favour of 

 which a strong probability pleads. In the desert east of the gulf of Tajura, at the mouth 

 of the Red Sea, one of the hottest and most detestable corners of the globe, a lake has 

 recently become known to European geographers, the Bahr Assal, which is marked by 

 the feature we are noticing. It is about six or seven miles long, and partially fills a 

 deep hollow in a country of volcanic formation, being 570 feet below the level of the 

 neighbouring sea, from which it is divided by a belt about six miles across. The waters 

 are extremely salt, and are constantly receding by evaporation under the action of the 

 intense heat, for when the British mission to Shoa had a day's bivouac in this terrestrial 

 pandemonium, the mercury in the thermometer stood at 126. The depression of the 

 level of this lake is thus conjecturally, but in a natural and simple manner, accounted for 

 by M. Rochet d'Hericourt. The depth of the innermost basin of the gulf of Tajura is 

 not less than 600 feet, or 120 feet below the surface of the salt lake. He supposes the 

 lake to have been anciently a part of the gulf, and to have been dyked off from it by 

 volcanic action. Receiving no fresh water, except after rains, it has been gradually 

 diminished by evaporation, and five hundred cubic feet of depth may be supposed to have 

 been lost since the upheaving took place. According to this conjecture, the bed of the 

 lake and of the adjacent sea are on the same level, but the surface of the lake has been 

 reduced below that of the sea, in the lapse of years, by the evaporation of a torrid climate, 

 acting without sufficient compensation. 



In striking contrast with the depression of these lakes, is the height of others in the 

 following table, which exhibits remarkable variations. 



Feet above Feet above 



the Level the Level 



of the Sea. of the Sea. 



Killarney, Ireland - ' ' -V 50 



Neagh, ditto r ' .^' ( " > 48 



Corrib, ditto '+ 16 



Erne, ditto - 140 



Derg, ditto - - 98 



Allen, ditto - 160 



Skene, Scotland - 1300 



Wetter, Sweden - 288 



Wener, ditto . 144 



Strand, Norway - - - 1187 



Miose Vand, ditto - 1576 



Oresund ditto ... 2400 



Superior, North America - - 623 



Huron, ditto - - 591 



Erie, ditto - - 565 



Ontario, ditto ... 234 



Michigan, North America - - 594 



Nicaragua, Central America ;t* >- 134 



Titicaca, Peru - 13,000 



Constance, Switzerland - - 130 



Geneva, Switzerland - 1152 



Neufchatel, ditto - 1437 



Lucerne, ditto - 1320 



Annecy, ditto - 1460 



Zurich, ditto - 1279 



Maggiore, Italy '.* - - - 640 



Como, ditto - - 650 



Iseo, ditto ... 630 



Garda, ditto - - 256 



Albano, ditto - 919 



Nemi, ditto "-' - -' 1022 



Van, Armenia ''* : - 5467 



4. The last class of lakes have both affluents and outlets. These are the most 

 numerous. They are sometimes formed by a number of streams flowing into a central 

 basin, from whence the superabundant waters escape by one principal outlet, or they 

 occur in the channel of a great river, and are the receptacles of its waters, which re-issue 



