98 G^LACIAL GEAVELS OF MAINE. 



15 feet. South of this point the glacial river crossed the valley of the Mat- 

 tawaiTikeag- River. No sand or gravel is visible in the valley for half a 

 mile or more; such deposits may perhaps have been laid down and have 

 been washed away by the river or covered out of sight by its alluvium. 



At Kingman there is an excellent opportunity to compare the shapes of 

 the stones of the glacial gravels with those of ordinary stream gravels. The 

 Mattawamkeag River at this place has cut down through a broad ridge or 

 sheet of till to a depth of 30 or 40 feet, and has deposited the stones of the 

 eroded till as a narrow plain of valley drift extending down the valley for 

 about one-fourth of a mile. A series of rapids existed at this point before 

 the building of the dam; and directly after the melting of the ice-sheet, 

 when the fall must have been 30 or more feet higher than at present, the 

 rapids and waterfalls must have formed quite a cataract. AVhile the deep 

 cut was being eroded the stones of the till must have been subjected to 

 much more abrasion than is common except in case of the steeper mountain 

 valleys, yet they preserve their till shapes very well. Their surfaces are 

 polished, and the apices of the angles are more rounded than those found 

 in the beds of the rivers and streams of Maine, except near the White Moun- 

 tains and in the valleys followed by the glacial rivers. Their shapes are 

 far nearer the angular and subaugular shapes of the tillstones than those 

 of the glacial gravel. As one sees how much more rounded the stones of 

 the osars are than this stream gravel at a place favorable to attrition, he can 

 not fail to be impressed with the great amount of attrition and frequent 

 changes of position to which the stones of the osars owe their shapes. The 

 alluvium of the Mattawamkeag River consists of fine sand and clay, except 

 for short distances near the rapids and waterfalls. 



The dam at Kingman originally extended from a bank of solid till on 

 the north to the terrace of rolled gravel, cobbles, bowlderets, and bowlders 

 before described. Twice in time of high water this loose gravel on the 

 south side of the river has been undermined and eroded by the water fall- 

 ing over the dam until the water escaped around the south end of the dam. 

 It thus happens that the dam is now twice as long as it was originally and 

 the channel is much broader at the dam than it is a short distance below. 

 At the time of my visit the water was flowing through three chutes near the 

 bottom of the dam, situated at intervals of about 12 feet. Between these 

 swift streams two ridsres of coarse g-ravel had collected beneath the water. 



