The Charles River in Massachusetts —Clapp. 225 
It is extremely probable that before the reversal of the 
Sudbury drainage the Assabet river was tributary to the Sud- 
bury through either Pantry or Hop brooks ; and thus the entire 
area now comprised in the Sudbury and Assabet basins drained 
into the Charles, which must, therefore, have been a stream of 
considerable size. 
Upon reaching the Boston basin the buried valley of the 
ancient river probably turns northeastward, passing beneath 
Wellesley to the valley of Rosemary brook west of Highland- 
ville, and thence northwesterly, to the present river below New- 
ton Lower falls. An interesting problem is presented by the 
broad valley of the present river lying east and northeast of 
Needham. This valley is situated on the western end of the 
West Roxbury slate belt (plate 13), and at Highlandville is 
separated from the preglacial valley of the Charles only by a 
high sand-plain, which for a mile north and south, is entirely 
free from outcrops (fig. 5). Between Highlandville and West 
Roxbury numerous borings have been made, some of which 
extend as much as 35 feet below sea-level without reaching 
bed-rock. To account for this ancient valley it has been sug- 
gested that the preglacial Charles may have flowed eastward 
along the slate belt across West Roxbury and Dorchester, thus 
making nearly a straight course from Wellesley to Boston bay. 
| have considered this view, but have been able to find no direct 
evidence to sustain it. 
Tide-Water Portion of the Charles—At the mouth of 
the Charles, as at the mouths of many of our seaboard rivers, 
there is a deep buried gorge which exists as evidence of the 
great Pleistocene elvation of the land, and its subsequeni sub- 
sidence carrying the river beds far below sea-level. That such 
is the case is shown by numerous artesian well and other bor- 
ings in Boston and vicinity.* Between the Back Bay district 
and Old Harbor, north of South Boston, wells have been 
bored to depths as great as 160-170 feet below sea-level be- 
fore reaching bed-rock, indicating that beneath this part of 
the city lies a deep east-west gorge. North of this depres- 
sion the bed-rock is shown to rise, until near the present river 
north of Beacon hill it reaches sea-level. Moreover, in Cam- 
ee 
*Geological History of the Charles River, Technology Quarterly, vol. xiv. 
No. 3, p. 199. 
