ae 
TARR AND WOODWORTH: CHANGES OF LEVEL AT CAPE ANN. 187 
the present beach, and from 500 to 700 feet inland, is another bar 
reaching an elevation of 41 feet and sloping away from the crest in both 
directions. It is flanked by a swamp about 15 feet lower than the crest. 
Its form is distinctly that of a beach, and cuts that have been made in 
it prove it to be composed of well-stratified materials. The surface is 
strewn with large water-worn pebbles resembling those of the modern 
beach. Back toward the northwest, the bar broadens until it reaches 
the base of some low rocky hills (Plate 5) which have the appearance 
of having been stripped of their drift cover. The base of this series of 
rocky hills is from 42 to 47 feet above mean tide level. 
If the land could now sink far enough to permit the waves to wash 
the base of these rocky hills, all the land at present to the seaward of 
them would be below the water, although some places, especially at the 
eastern end of the bar, would reach almost to the high-water mark. 
Assuming that nothing had been stripped from any of the hills, the con- 
dition would then be a coast line at the western margin of the bar and a 
series of shallows at the eastern margin. The prevailing direction of 
effective waves approaching such a coast then, as now, would be from 
the northeast. Breaking upon the shoals of the eastern end they would 
remove whatever loose fragments were available, and drive them toward 
the southwest. The loose fragments derived from the western margin 
would be driven onward toward the south and, as the waves advanced 
into this more or less completely enclosed arm of the sea, one would 
expect them to build a crescent-shaped beach similar to the crescent 
beaches which are so common along the coast. Indeed, the beach at the 
present sea level (described above) is such a crescent bar forming a bar- 
rier which has cut off Niles Pond from the sea. 
Another elevated beach, in some respects resembling the one just 
described, is found west of High Pebble Beach (D, Plate1). It faces the 
northeast, and skirts a line of rocky hills on the north and south sides, 
while on the west side it stretches across as a bar (Plate 7) from the 
hills on one side to those on the other. Its form is well shown ona the 
accompanying map, also made for Mr. Gardner by Professor Burton 
(Plate 4, B). The crest of this bar is 52 feet above the present tide level. 
The fact that it is higher than the bar just described is doubtless due to 
its exposure. In the case of the beach first described (Plates 2 and 3), 
the waves from the northeast must have been greatly interfered with 
by shallows, and possibly at first by low islands; but the beach back of 
High Pebble Beach was exposed to the full force of the northeast waves. 
Its form is well shown not only on the map (Plate 4), but also in the 
