The Charles River in Massachusetts—Clapp. 221 
on the crystalline areas must have so adjusted themselves as 
to take the most direct courses to the basins. 
At the close of the Tertiary period occurred the great ele- 
vation of the land, probably amounting to several thousand 
feet in this region, which is supposed to have ushered in the 
Glacial epoch. This increased the energy of the rivers, so 
that in the bottom of their valleys they cut deep gorges. The 
gorge at the mouth of the Charles is from 100 to 200 feet 
deep—below the present sea level. During the ensuing gla- 
ciation thePleistocene gorges and some of the Tertiary valleys 
were filled and obliterated by the extensive drift deposits. Thus 
with the disappearance of the ice, the streams rarely assumed 
their former courses, but instead found new channels across 
the drift-covered surface in utter disregard of the pre-glacial 
conditions, 
The Charles River Described. 
Rising in the village of Hayden Row, Hopkinton, the river 
flows for the first few miles almost directly southward. The 
valley south of Milford is broad and evidently old. But just 
west of Bellingham a sudden bend occurs, and the direction for 
the next few miles is eastward, the stream crossing the north- 
south ridge of land through a much narrower and younger 
valley. Northeast of Bellingham it turns sharply to the north 
and for several miles flows slowly through broad meadows; 
but at Medway it is suddenly transformed into a torrent which 
dashes for half a mile through a deep and rocky ravine. 
Flowing out of this narrow gorge, the contrast is very 
great, as a broad open valley is reached, entirely devoid of rock 
outcrops, and with every appearance of being very old. At 
Rockville another change occurs, and for four miles the course 
is northeast, without a continuous well-defined valley. Near 
the mouth of the Stop river a broad valley is again encountered, 
and in it the Charles flows northwest through broad meadows, 
(fig. 2), nearly to South Sherborn. Here there is another 
turn to the north, and for the next six miles the stream winds 
about between hills and ledges. 
Below South Natick we pass from a region of frequent 
outcrops to one where they are very scattering, and once more 
reach a short portion of the valley which is undoubtedly very 
old. At Charles River village ledges are again encountered 
