PART I. CHAPTER II. 



33 



Ripple Mark, how formed. 



is thrown down upon it, conforming nearly to its surface. After- 

 wards the other layers, 2, 3, 4, may be deposited in succession, 

 so that the bank B C D is formed. If the current-then increases 

 in velocity, it may cut away the upper portion of this mass down 

 to the dotted line e (Fig. 4.), and deposit the materials thus 

 removed farther on, so as to form the layers 5, 6, 7, 8. We have 

 now the bank B C D E (Fig. 5.,) of which the surface is almost 



Fig. 5. 



level, and on which the nearly horizontal layers 9, 10, 11, may 

 then accumulate. The opposite slope of the diagonal layers of 

 successive strata, in the section Fig. 3., may be accounted for by 

 changes in the direction of the tides and currents in the same 

 place. 



Fig. 6. 



Slab of ripple-marked (new red} sandstone from Cheshire. 



The ripple mark, so common on the surface of sandstones of 

 all ages (see Fig. 6.) and which is so often seen on the sea-shore 



