320 



CAPE COD GEOLOGY 



granite and gneiss, there is exposed above sea level along the cliffs a thin bed 

 of sand overlying a blue clay. The clay at the surface is in places whitish, but 

 that within the bed is ferruginous red. This clay is probably the equivalent of 

 the Gardiners clay. 



A well that was driven to a depth of 230 feet on the island passed through 

 sand and blue clay. The water in this well rises to a height of 190 feet above 

 the bottom of the boring. 



Freshwater swamps occupy several small tracts on the island, the water 

 being held up by the underlying clay. Saltwater marshes have been formed in 

 the lee of the barrier beaches and around the shores of the salt ponds. The 

 Coast Survey chart of 1853 shows West End Pond extending into confluence 

 with a small pond that was cut off from it by a marsh as shown by the survey 

 of 1889. 



The southwest coast of Cuttyhunk is exposed to heavier attacks by the 

 sea than any other part of the coast of the Elizabeth Islands and has therefore 

 retreated rather rapidly since the first survey was made. A comparison of the 

 chart of 1853 with that of 1889 appears to show that the south coast has re- 

 treated more than 130 feet, or at a rate of more than 3 feet a year. A few centuries 

 ago the land must have extended farther south and west. 



SOW AND PIGS REEF 



A boulder-covered reef extends westward from the westernmost part of 

 Cuttyhunk to a group of large boulders known as the Sow and Pigs, a map of 

 which was made by Lieut. M. Woodhull, U. S. N., in 1853, which accompanies 

 his report on the Sow and Pigs rocks. 1 



Lieutenant Woodhull states the Sow and Pigs rest on ' '& bed of rocks and 

 stones from the size of those generally used for paving, to boulders two or three 

 feet in diameter." He says that the cluster which makes up the "pigs" forms 

 almost a circle, about 50 feet in diameter, within which there is one to two feet 

 of water at low tide. No. 1, or Saddle Rock, measured 14 feet in length, 7 in 

 width, and 9 in height. Sow rock stands on the south slope of the reef in about 

 two fathoms of water at low tide. The base of this rock, according to Lieutenant 

 Woodhull, measured 15 by 20 feet, but the apex was visible only at low water. 

 The Sow and Pigs reef is no doubt the site of a former islet, and the Middle 



"■Woodhull, M., Upon the survey of the "Sow and Pigs" rocks, off Cuttyhunk, Massachusetts, with 

 reference to the location of a lighthouse, Rept. Supt. Coast Survey for 1853, p. 172, Plate No. 5, Sketch 

 A, No. 5. 



