228 The American Geologist. April, 1902. 
it. The lower portion of this beheaded stream is represented 
today by Stony brook, which has never been of sufficient size to 
make a large valley. One of its branches, the infantile Charles, 
flowing northward from Needham through the Boston basin, 
cut backward toward the south, and on account of its location 
on the softer rocks, deepened its valley below that of the east- 
west stream (the possible Wachusett). This river was re- 
tarded in its erosion by the crystalline areas across which it 
flowed, making possible its capture by the Charles. Thus, ex- 
cept for several minor tributary streams, the Tertiary valley 
between Wellesley and Hyde Park was left dry. The valley 
northeast of Needham was probably formed by a tributary 
to the Charles which cut backward from Highlandville along 
the slate belt to the east. 
Another great Tertiary stream draining the area under 
consideration was the Baggistere, which rose in the vicinity 
of Sherborn and flowed east and then northeast to Boston 
bay through the Neponset valley, which is shown by its great 
size to have been occupied at an early date by a large stream. 
The Neponset river, flowing entirely upon sedimentary rocks, 
was able to cut back its valley for a considerable distance, 
the limit probably being reached in the vicinity of Nor- 
folk, where, as indicated by the topography, a tributary of Nar- 
ragansett bay had its source. At first the south-flowing streams 
in this vicinity may have run directly across the crystalline 
area between the Norfolk and Narragansett basins; but in 
time they must all have been diverted to the easier outlet 
through the connecting pass at Wrentham. Thus the Norfolk 
basin became occupied by two main streams, flowing in op- 
posite directions from the watershed at Norfolk. The minor 
streams having their sources on the large crystalline area to 
the north then so adjusted themselves as to take the most 
direct courses to the main streams in the basin. It is probable, 
however, that little adjustment was necessary, as the basin 
lay directly across their seaward paths. 
The Tertiary changes outlined above were undoubtedly 
much more complex; but this appears to be the simplest se- 
quence of events which could have brought about the conditions 
existing at the beginning of the Pleistocene period. The 
preglacial streams deduced from present conditions are found 
