iS05-] -491 [Abbe. 
All the material of the beaches does not, however, come from 
the bottom. Where the mainland has a sufficient depth of watei- 
off its coast the waves have attacked it directly and carved out 
cliffs, or the landward migrations of the bars may cause the 
locus of maximum activity to intersect an irregularity of the 
mainland coast and thus a cliff is formed flanked by sand bars. 
In either case, tidal and other currents moving along the face 
of the cliff transport a portion of the debris from it to the 
beaches and bars foi-ming on either side, while the remainder is 
carried seaward or remains as a beach in front of the cliff. 
These currents niay be of tidal origin or they may be set up by 
winds or by waves coming obliquely to the coast, as the .Atlantic 
rollers do on the Carolina coast. 
Along our Atlantic coast the general drift of these long shore 
currents seems to be southerly. This conclusion is reached 
because as we go southward we find that the quartz grains of 
sand lose the angular shape they have in the north and become 
more and more rounded. Again, obsei'vations on the passages, 
kept open thi'ough the bars by the tide, show that they also tend 
to migrate southward. Professor Shaler says ^ : "In the longest 
connected lagoon of the American coast — that on the eastern 
shore of Florida known as the Indian River — each inlet, for 
the reason that the sands of the island beaches are constanth^ 
mo\dng southward, gradually travels in a southerly direction 
until it abuts against some obstacle. Then the further incursion 
of sand from the north closes the opening" (p. 126). ''The 
southward movement of the sands along this shore is indicated 
by the existence of hooked spits, such as that at the south end of 
Chincoteague Bay, and again in a more extensive way at Cape 
Charles" (p. 175). Speaking of the sand on Cape Florida he 
says : " At this extreme southern position the quantity of the 
sand is not great and the grains of silex of which it is composed 
are much rounded by their long and arduous journey . . ." (p. 
12S). 
This current ^-ith its load of sand, b}^ dropping some here in a 
hollow or cutting away part of some irregular protrusion, event- 
ually establishes, along the seaward face of cliffs and bars, an 
1 Thirteenth annual report, U. S. geol. survey for 1891-92. 
