CORRASION BY GRAVITY STREAMS. 293 



generally represented by meadows through which the valley 

 stream meanders. (See also Johnson quoted in literature.) 



The well developed meadows in the valley " narrows" or 

 constrictions are associated characteristically with high 

 and steep opposing walls not set widely apart. These walls 

 may be from 1,000 to 2,500 feet in height, and they reveal 

 the action of one dominant agency in the formation of their 

 present peculiar profiles. Above the steep walls another 

 set of similar profiles may often be seen but of less steepness. 

 Strong horizontal groovings occur in the valley constrictions 

 especially on massive wall buttresses or on projections 

 near the channel base. These grooves often parallel each 

 other, and are as much as from six to ten feet in depth. 

 Heavy undercutting occurs on the cliffs of a " narrow " when 

 facing the direction of heaviest ice motion during the recent 

 glacial period or periods. Hanging valleys occur here also. 

 The main and tributary valley "steps" approximate to 

 the cirque or amphitheatre shape and the valley heads 

 themselves are represented by magnificent cirques. The 

 "meadows" observed in the pronounced valley "broads" 

 are associated with large moraines. 



Another common feature is the existence of small cirque- 

 like forms on the down-stream aspect of salients and high 

 valley shoulders. Quarrying has occurred here, while 

 strong abrasion characterises the upstream aspect. (This 

 quarrying and abrasion is also noticeable on the down- 

 stream and upstream aspects respectively of valley"steps"). 

 Scratching and polishing by ice characterise the waning 

 action of the glaciers. 



Steep sided canons are commonly enveloped by some- 

 what similarly shaped and similarly situated forms. This 

 gives rise to "valley in valley" (or "canon in canon") types 

 terminated headwards by "cirque in cirque" forms. The 

 older enveloping cirques have flatter profiles than the 



