18 ON CHANGES IN THE DISPOSITION 



should we easily recognise one feature of the countries 

 most familiar to us. 



Of the filling of lakes, the whole world presents 

 examples, and we see the process going on every day. 

 Being a subject which concerns physical geography, 

 we may procure abundant information on it, in the 

 works of antient and modern geographers. The boun- 

 daries of the Caspian are every day contracting, and 

 the neighbouring deposits of shells and mud indicate 

 its former probable communication with the Aral. The 

 Baikal is diminishing rapidly : and the valley of Cash- 

 mire still contains some small lakes, the remains of 

 that which once filled the whole of this basin : as is 

 equally supposed of the valley of Nepaul. In Mexico, 

 in 1520, Cortez found two lakes, the one salt and the 

 other fresh : there are now five smaller ones, produced 

 by the accession of new land ; and the whole valley, 

 containing two hundred and forty-four square leagues, 

 of which but one tenth is now water, was formerly a 

 single lake. Here, I need scarcely repeat, we trace 

 the origin of those lacustral " formations," concerning 

 which geologists have made such confusion ; as, in the 

 cases just quoted, we equally find those alluvia of the 

 ocean which have so often been confounded with them 

 under the term "Tertiary." If I unwillingly take room 

 for further examples, since thus are books too easily 

 written, teaching nothing, as is the usage, the same is 

 true of the lake of Geneva, diminishing daily ; of those 

 of Thun and Brientz, now separated by an alluvial 

 plain ; of the valley of the Aar, once a receptacle of 

 water ; of Loch Tumel, in our own country, now re- 

 duced to less than half its original size ; of Loch Ran- 

 noch, once flowing at the foot of Mount Alexander ; 

 of Crummock and Buttermere, now separated like the 

 Swisslakesjust mentioned ; and of Loch Lomond, where 



