» 24 = 
50 to 100 feet lower than that of the plain. Presumably, this gravel 
is continuous with that of the plain. As may be seen along the west- 
ern side of the Buzzards Bay moraine, its surface beneath the till 
is not smooth like so much of the plain, however, and great angular 
blocks are embedded in- it here and theres Therefore, it is believed 
that these portions of the plain, now buried under the moraine, were 
originally the ‘marginal+portions of the great fan as it was con- 
structed during retreat of the ice before readvance produced the 
overlying moraines Such portions were’‘deposited on and around irreg- 
ular masses of ice at the ragged edge of the ice sheet. Shifting 
currents, such as would: result from movements of water over this 
rough and changing landscape, deposited layers sloping at unsystem- 
atic anzles. The irregularity of the surfacé increased as the buried 
ice melted. Angular blocks from the ice fell and slid onto the srav- 
el at some placese : 
Source of the Meltwaters 
The water which tuilt the pitted plain carried some fragments. 
of rock like those found in both the Sandwich moraine on the north 
and the Buzzards Bay moraine on the weste Counts of the number of 
different kinds of rocks among 200 pebbles selected at random at» 
each of 12 locations bear out this subjective observation made at 
innumerable pits (Table 2a). Only one stone count, that from a pit> 
west of Péters Pond in Forestdale near the pouchwesccrs corner of the 
Sandwich quadrangle, is closely Similar to counts in the Sandwich 
moraine, and only two stone counts, one made west of the Massachu- 
setts National Guard camp on Turpentine Road near the center of the 
Pocasset: quadrangle, the other almost half a mile east of Shallow 
Pond on-the north side of Mill Road in the northwestern part of the 
Falmouth quadrangle, are much like counts in ‘the Buzzards Bay mo- 
raine. The average of all pebble counts from the plain shows a pro- 
portion of granites, diorites, and basalts like that of the Buzzards 
Bay moraine, whereas the proportion of volcanic and quartzite peb- 
bles is like that of the Sandwich moraine. Because the proportions 
of several types of rock containéd in the two moraines are signifi- 
cantly different, as may’ be seen in Table 2b, itis concluded that 
the water “that bore gravel to the pitted plain: gathered. material 
from sources under both lobes of the ice sheet. - During transporta- 
tion these pebbles were fairly well commingledy 
The uniform slope of the plain to the south and southeast, away 
from the apex and in directions ‘parallel to each moraine front, shows 
that a -considerable part. of the water entered the plain somewhere 
near or at the present apex, rather than here and there along the 
line of the moraines, At two localities, one located half a mile 
southeast of Sigral Hill and about a mile northwest of the certer of 
the Pocasset quadrangle and the other just north of Falmouth near 
Grews Pond, the plain shows a marked slope away from’the bordering 
morainee. In the first of these ‘the'deposit is made of sand and is 
shaped like a small fane At the Falmouth locality it is made of 
coarse gravel already described in discussion of the Lawrence 
’ 
