The Charles River in Massachusetts.—Clapp. 219 
tinuing across Medfield to Boston bay? Why does it not fol- 
_ low a direct course across Wellesley to Riverside, a distance of 
three and a half miles, rather than its actual course of twenty 
miles by way of Dedham? Again, upon reaching Dedham, 
why does it not flow straight to Boston bay, instead of bend- 
ing back towards Newton? 
Third.—To trace the ancient courses of the river and de- 
termine the causes of the various stages in its development. 
Fourth—To explain the relation of the river and its tribu- 
taries to the geological structure of the region. 
Fifth—To determine the position of the Charles in the 
systematic classification of rivers. 
General Topography and Geology of the Region. 
As the goverment topographical map shows, the land about 
the extreme headwaters of the Charles river attains a maxi- 
mum elevation of 600 feet, but elsewhere in this basin the high- 
est hills range from 300 to 460 feet. Professor Crosby has 
shown that the few rock hills of these hights in eastern Massa- 
chusetts are remnants of the Cretaceous peneplain. Between 
them the Tertiary peneplain is developed with an elevation of 
from 100 to 200 feet; and in this less mature plain the valleys 
of the Charles and its tributaries have been carved. 
The source of the brook which is considered the head of the 
river is at an elevation of about 500 feet. As shown by the 
profile on plate 14, the descent in the upper part of the stream 
is comparatively rapid. It crosses the 400-foot contour but one 
mile and the 300--foot but three miles, from its source. The 
200-foot contour is crossed at Bellingham, twelve miles from 
the source, and the 100-foot below Natick, about midway in 
the length of the river. Looking at the profile more in detail, 
several points are noticed where the fall is concentrated. At 
Medway there is a descent of 27 feet in a distance of half a 
mile. The descent at Newton Upper falls is 25 feet in a quarter 
of a mile, and at Newton Lower falls 22 feet in about the same 
distance. Between these points of rapid fall there are long 
stretches where it is very slight indeed. Two of these stretches, 
one between Rockville and Natick, and the other between 
Charles River village and Newton Upper falls, are especially 
noticeable. 
In general, the main valley of the Charles is broad, and 
obviously very old, but at several points, as at Medway and 
