Pleistocene Geology of Moravia Quadrangle 369 
so frequently and accurately described^® that no further reference 
is needed here. 
(3) Ridges, There appears in all the valleys studied a per- 
sistent form of drift which it seems most natural to classify under 
this heading, although the name is not at all suggestive of origin 
or development. They consist more frequently of till; but gravel 
sections occur in many of them. They vary much in length, the 
longest one noted measuring about one-half mile, while the general 
length is less than twenty rods. 
In general direction these ridges are either transverse or longi- 
tudinal. As to their method of formation they may be construc- 
tional or destructional. As a general condition, however, this 
form of valley drift is found near the foot of the valley walls, 
seldom out very far in the flood plain. 
One form of the constructional type is shown in figure 10. This 
was made of debris accumulating along the margin of the valley 
tongue, and consists largely of till. The northern end of this 
ridge resembles a kame; southward the ridge has lost its original 
height through slumping to both sides. A longitudinal section 
shows a decline from 60 feet at the north to zero at the south; the 
sides at the higher part slope 24° to 26°. Clay predominates in 
the southern part, whereas gravel increases towards the northern 
end of the ridge. 
Another constructional form of ridge may be developed in the 
j distal area of a valley lobe which, following a period of less activ- 
ity, has developed openings or crevasses in consequence of an 
i advance the ridges represent the concentration of debris by 
ji streams. Glacial drainage is not connected with this particular 
1 type of drift save when very near the edge of the ice. It fre- 
I quently happened that tributary valleys were occupied by the 
1 lateral tongues of ice which in position were transverse to the 
1 drainage flowing from the north along the margin of the ice lobe. 
In this condition probably the stream for some distance had its 
I bed over the ice which thus reached out into the tributary valley. 
! That a super-glacial course of streams always hypothecates such 
I an arrangement of valley lobe and lateral tongue is not implied. 
Chamberlin: Third Ann. Report,X^. S. Geol. Surv. (1883), p. 304. Gilbert: 
Monograph /, U. S. Geol. Surv. (1890), pp. 81-83. Tarr: Phys. Geog. of New 
Tork State (1902), p. 85. 
Tarr: Zeitschrift fiir Gletscherkunde^ band iii (1908), p. 99. 
