48 



LAKES OF NORTH AMERICA. 



When a structure like that described above is incomplete and projects 

 from the shore like an unfinished railroad embankment, it is termed a spit. 

 An illustration of such an instance observed on the shore of An Train 

 island, Lake Superior, is shown in Plate 11. See also Plates 2, 3 and 4. 



When an embankment 

 spans the entrance of a bay- 

 so as to shut it off more or 

 less completely from the 

 main water body, it is 

 termed a har, in accord- 

 ance with the custom of 

 mariners in designating 

 such obstructions to navi- 

 gation. Maps of bars on 

 /4^^^sg^ >^ '%^ the shores of lakes Su- 



perior and Ontario are re- 

 WC\^^rlf^\\ produced in Figs. 5 and 



^S»t^^ -> ^Z- v' \ > 6, from the maps of the 



U. S. Lake Survey. The 

 manner in which these 

 were formed, as well as 

 their various modifications 

 FIG. 5. -MAP OF SAND BAKs : WEST END OF LAKE suPEUK^K. ^f o^^tliue aud the prescncc 



of channels across -them in certain instances, will be understood from the 

 description of a more simple example just given. 



The end of a spit is frequently turned toward the shore, owing to a 

 deflection of the current that built it, or to the opposing action of two 

 or more currents, and becomes a liook, as is illustrated on Plate 12. 

 Again, where the hook is more pronounced and the distal end of the 

 structure touches the shore, as happens occasionally when there are only 

 slight changes in the direction of the coast line, a loop-bar or V-har results. 



In brief, it may be said that the waves and currents of lakes have 

 the power of excavating cut terraces along the shores confining them and 

 of carrying away the waste from the cutting, together with similar mate- 

 rial contributed by streams, and of building it into terraces and embank- 

 ments of various forms adjacent to neighboring shores. 



Deltas. — Where streams bring to a lake more detritus than is carried 

 away by shore currents, accumulation takes place and an addition, termed 



