CHAPTER VIII 

 LAKES 



Many of the phenomena of the ocean are repeated on a smaller 

 scale in lakes. The waves of lakes and their attendant undertows 

 and littoral currents are governed by the same laws and do the 

 same sort of work as the corresponding movements of the ocean. 

 Tides are absent, or insignificant; but slight oscillations of level, 

 known as seiches, 1 have been observed in many lakes. They are 

 probably caused, in most cases, by sudden changes in atmospheric 

 pressure. While they are generally very slight, they sometimes 

 amount to as much as a foot, and occasionally to several feet. The 

 seiches are oscillatory movements, and their period is influenced 

 by the size and depth of the lake. They have been studied most 

 carefully in Switzerland. Currents corresponding to those of the 

 ocean are slight or wanting in lakes, but since most lakes have 

 inlets and outlets, their waters are in constant movement toward 

 the latter. In most cases this movement is too slow to be readily 

 noted, or to do effective work either in corrasion or transportation. 

 The work of ice is relatively more important in lakes than in the 

 sea. 



Changes taking place in lakes. The processes in operation in 

 lakes are easily observed and readily understood. (1) The waves 

 wear the shores, and the material thus derived is transported, 

 assorted, and deposited as in the sea, and all the topographic forms 

 resulting from erosion or deposition along the seacoast are repro- 

 duced on their appropriate scale in lakes. (2) Streams bear their 

 burden of gravel, sand, and mud into lakes and leave it there. (3) 

 The winds blow dust and sand into the lakes, and in some places 

 pile the sand up into dunes along the shores. (4) Animals of 



1 Forel, Compte Rendu, 1875, 1876, 1878, 1879, and P. DuBois, 1891. 

 Also Forel's Lac Leman. 



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