558 The Formation of Cape Cod. [September, 
ing five feet in diameter. The other locality is about a sixth of a 
mile west from Highland Light, where one block fifteen feet long 
and several others five feet long occur. In the north part of 
Eastham the modified drift forms extensive level plains about fifty 
feet above the sea. From South Wellfleet to High Head, in the 
north part of Truro, the contour on the west side of the cape is 
in very irregular small plateaus, ridges and hills, nearly uniform 
in their height, which varies from one hundred to one hundred 
and fifty feet above the sea, increasing from south to north. 
These enclose depressions from twenty to one hundred feet deep, 
many of which contain ponds. They are also intersected from 
east to west by broad valleys with steep sides, which have their 
bottom nearly at sea-level or below it. Examples of these are 
the hollow which extends from North Truro toward Highland 
Light, and that of Pamet river, which varies from a third of a 
mile to one mile in width, and cuts the cape quite across, its bot- 
tom, until recently dyked, being marsh overflowed by high tides. 
The east side of the cape, through Wellfleet and Truro, is 
a nearly continuous bluff, one hundred to one hundred and sixty 
feet high, horizontally stratified, being evidently a remnant of a 
nearly level plain, the east part of which has been washed away 
by the sea. This process is still going forward, exposing fine 
sections of these deposits along most of this distance. The 
material is mainly sand and fine gravel, with coarse gravel in some 
portions, containing pebbles and fragments up to one foot or 
rarely two feet in diameter. Less than a half dozen larger blocks, 
none of them, however, so large as four feet through, were seen 
in this whole line of cliffs more than fifteen miles in extent. At 
the base of these bluffs banks of darkish sandy clay occur in 
several places, rising ten to forty feet above the shore and extend- 
ing one hundred to five hundred feet in length. These beds 
enclose occasional pebbles up to one foot in diameter. At the 
Clay Pounds, close north of Highland Light, is a massive bed of 
somewhat similar sandy clay, bluish-gray in color, forty to fifty 
feet thick, extending a quarter of a mile to the west, as shown by 
wells, and the same distance along the cliffs to the north, where 
it gradually thins out. This deposit is finely laminated, level in 
stratification and free from pebbles. Its base is clearly seen in 
many places for an eighth of a mile holding a nearly constant 
Eh: of forty feet above sea-level, and is marked by a hard fer- 
