CAPE COD GEOLOGY 293 



1883 



Jan. Feb. Mar. Apr. May Jxne July Aug. Sept. Oct. Nov. Dec. 



N 14 12 14 10 10 8 9 6 8 14 13 14 



N. E 11 8 10 10 8 7 7 10 6 9 9 10 



E 10 1 12 8 9 6 3 7 5 6 12 11 



S. E 12 12 14 7 9 10 4 8 6 10 23 18 



S 18 8 15 12 14 10 8 8 9 11 9 10 



S. W 12 9 12 9 10 9 11 8 8 9 10 11 



W 13 11 11 5 6 6 4 6 6 9 9 11 



N. W 12 15 16 10 10 6 9 9 13 10 14 15 



1884 



N 11 10 10 



N. E 10 11 11 



E 11 6 8 



S. E 20 12 15 



S 12 7 9 



S. W 13 12 9 



W 11 12 10 



N. W 12 15 13 



The prevailing wind blows from the southwest, and as it is fairly dry it 

 probably does most of the cutting. The winds from the north, northeast, east, 

 southeast, and south are usually damp, and the moisture they form causes the 

 grains of sand to resist them so that only a strong wind from these quarters 

 can move the sand. 



The sand and dust blown from the lag-gravel tracts of the glacial drift form 

 conspicuous deposits only near the edges of cliffs, where the work of the wind 

 is reenforced by the vortical movements there set up. High dunes are formed 

 in such positions, and nowhere more abundantly in this region than in the 

 stretch on the outside of Cape Cod between Highland Light and Nauset Light, 

 just where the cliffs are highest and steepest. A belt of such dunes and associated 

 tracts of lag-gravel border the top of the cliff in Wellfleet and Truro for a con- 

 siderable distance north and south of the Pamet River coast guard station at 

 elevations as high as 100 feet above sea level where the older glacial gravel 

 attains this level. 



EROSION OF CLIFFS BY WINDS 



The wind loosens and tears down the incoherent gravel and sand in the 

 coastal bluffs. On fair days when dry winds are blowing in a favorable direc- 

 tion, pebbles loosened by the blowing out of the sand at their bases roll down 

 to a sandy talus. Many of these pebbles take somewhat curved courses, rico- 



