G. S. Kinahan — Formation of Ravines. 



407 



yearly the shed from the hills adds to the height of the banks. From 

 this would it not appear that previous to the formation of the drift 

 there was a stream in the valley fed, as it is now, by a spring ; that 

 the shedding from the hills came down yearly into the valley, but 

 could not fill it up as the stream always keeps its channel clear, 



Fig. 1. — Sketch showing Maum with an accompanying hank of recent Drift, a ravine being 

 seen in the latter. 



therefore the debris was gradually banked up, leaving a ravine in the 

 place that from the first was occupied by the stream ? What seems 

 to be in favour of this suggestion is the fact, that if one hill is higher 

 than the other, or one hill sheds more than the other, the bank of 

 the ravine, on the side next the hill that sheds most, will be highest ; 

 or, if one hill suffers but little waste, the drift will only occur, in 

 mass, on one side of the stream, steep on the stream side and tailing 

 from it for a considerable distance down the valley. Furthermore, 

 if there is a cross-section exposed in one of these drift-banks, as may 

 often be seen in road-cuttings and mining operations, it will be found 

 stratified and dipping away from the ravine, as represented in the 

 Woodcut (Fig. 2). 



Fig. 2. — Section of recent Drift-bank. 



Eecent Drift-banks also often occur below an escarpment near 

 the summit of a mountain range ; and although they are arranged 

 in ridges and hollows, yet there never could have been a head of 



