Lakes 291 



In volcanic regions lakes are not uncommon, generally of 

 a more or less circular form, and either occupying the site of 

 extinct craters or due to subsidences consequent on volcanic 

 eruptions; such are the Maare of the Eifel in Germany, and 

 many lakes in Italy and in the Azores. 



Lakes are not only widely distributed in latitude and 

 longitude, they also occur in all elevations. Indeed, as a 

 certain elevation above the sea produces an effect as regards 

 climate equivalent to a certain increase of latitude, we find 

 lakes existing in the centre of continents, and on high plateaus 

 and mountain ranges, in latitudes where they would be speedily 

 dried up if at the level of the sea. Many of the lakes in Scotland 

 (as Lochs Lomond, Morar, Coruisk), of Norway, of British 

 Columbia, and of southern Chili are raised only by a few feet 

 above the level of the sea, and are separated from it often by 

 only a few hundred yards of land, while in the Cordilleras of 

 South America we have Lake Titicaca 12,500 feet, and in 

 Asia Lake Kokonor 10,500 feet above the sea. Many lakes 

 whose surface is raised high above the level of the sea are so 

 deep that their bottom reaches considerably below that level. 



Dimensions of Lakes. The principal measurements con- 

 nected with a number of lakes in different parts of the world, 

 presented in the table, p. 292, will give a more precise idea 

 of the size of the lakes than could be given by description alone. 

 ;ii this table it will be seen that by far the largest con- 

 tinuous sheet of fresh water is the group of North American 

 lakes, and of these Lake Superior is more than double the size 

 iy of the others ; this is principally due to its great breadth, 

 i- vrry little longer than Lake Michigan. Lake Superior 

 communicates with Lakes Michigan and Huron, which are 

 l)i. UK -lies of one and the same lake, by the St Mary's 

 49 feet fnmi Superior to Huron. Huron 



emptier itx.-lf into Erie by the St ('lair river. Lake St (Ian. and 

 tm.illv the Detroit river. Lake Erie overflows by the Niagara 

 1 falN into Lake nntaiio, \vhenee the water fin. illy i^ 

 conveyed to the sea by the St I.i\\nnrc. The area of tin- 

 lakes together is in round numbers 100,000 square milrs. and, 

 it that of the St Lawrence and it be added, the water 



192 



