1)4 



C.KOl.OMCAI. IIISTOIJV OV LAKK 1,A1I()NTAN. 



tidii (if a i^cnlh- slopinn' lake iiiai-L^in adjaci'iit to a l)ay is represented. 'I'lio 

 I'uri'eiit in sweepiiij^' aloiij;- tlie slielviiii>' slioro in the directidii iiidicatt'd liy 





Kli!. 11,— 111. Ill liliili' illunlnilMi;; Ilii' I'uniKilii.n ul' .iiilHiiiKuii'lits. 



the arrow, will eari\- with it a, narrow liand of slior(Mli-it't ; when the en- 

 trance to the lia\' is reaehed the direction ol" the ciirront is but little changed; 

 it consi'ciuently enters deeper waters where its vidocitv is checked and its 

 load oi" (h'-hris deposited. Frosli material continues to be swe))t alouj^' the 

 shore terrace and is added to that alr(>ady accunudated until !i long, narrow, 

 level-topix'd enibanknient is built up. Current-fornied structures of this 

 nature have the character of a railroad enibanknient, and soiiietiines grow 

 to be miles in ](Migth and perhaps several hundred I'eet high. Should the 

 t'onditions represented in the sketch continue long enough, it is e\idciit that 

 the b.iN' will i'\'entiiall\' be cut oil' iVoni the lak(^ and torin a lagoon ; in such 

 an instance it is tretjueutly convenient to speak of the structure as a bay- 

 enibankinent. In case the bay chances to bo nt the mouth of a stream, tho 

 embankment may become breached by the outflowing waters and rej)aire(.l 

 again bv the currents, thus complicating tho stratiilcation of the deposit. 



Knilianknieiits. like barrier bars, when exposed in cross section present 

 a more or less peitect anticlinal structure due to the mode ot tlu'ir deposi- 

 tion. \\'lien buried beneath subsequent deposits, as laeiistral beds, for ex- 

 ainph", and dissected by erosion, tliev soinetilnes simulate a true anticlinal 

 formed by the folding ot' the strata ; an instance of this natun> is illustrated 

 on Plato XX^^ 



Simple embankments, like that shown in the above illustration, are usu- 

 ally either straight or but slightly curvt'd, and end at the distal e.xtremity in 

 a semicircular scarp the slope of which depends on the angle of stability in 

 water of the material of which the structure is com])osed. IV'vond the end 

 of tho embankment sand-banks are commonly fi>ruu'il liy the subsidence of 



