89 



]\Iuch of the sand now Ibtind in the beaches along the 

 shore of Lake Erie was derived from the drift deposits left 

 b}' the ice. Onh- a comparatively small portion of this 

 beach material has a local origin, having been worn by the 

 waves from the shale cliffs. The material thus derived, is 

 readily recognized b}^ the flat thin character of the pebbles 

 composing it, a feature which early caused it to be known 

 by the name of "flat gravel." (See Plate XIX. ). 



The cliffs of unconsolidated material are of course much 

 more readily eroded by the waves, than the shale clifts. The 

 active destruction of the drift cliffs can be seen at a great 

 many points along the lake shore, and it is frequently 

 emphasized by the trees, which, losing their foot-hold as the 

 clift is being undermined, slide down the banks. 



The sands derived from the clifts are carried away by the 

 long-shore currents, and deposited where the force of these 

 currents diminishes. Thus, bars are thrown across the 

 mouths of all the streams and inlets, and sand-spits run 

 out from the headlands, menacing the safety of the coast 

 navigator. 



The beaches iDetween the headlands vary in the character 

 of their material, as well as in the angle of the slope facing 

 the water. Where the water deepens rapidly oft'-shore, so 

 that the large breakers roll in and reach the shore, the 

 material of the beach is usualh' coarse gravel, and the front 

 slope a steep one, the beach often assuming a terrace form. 

 Where, however, the water is shallow for a considerable 

 distance from shore, or where a submerged sand-bar causes 

 the breaking of the great waves long before they reach the 

 shore, the beach is usually of a sandy character, and the 

 slope a gentle one. In the flrst case ( that ol the deep water) 

 the fine material is carried out by the undertow, so that 

 onlv coarse material remains. This will naturally retain 

 the steep slope given it by the great waves. In the second 

 case (that of the shallow water) the sands dropped by the 



