OTHER TERRACES 45 



within the gorge. Lil^ewise terraces remain above the sides of the gorge. 

 The retreat of the falls, and hence the direction of the gorge, appears to 

 have been influenced somewhat by the direction of the joints in the lime- 

 stone beds, so that the course of the river preceding the falls' recession is 

 not exactly followed by the gorge. 



Most of the terraces have been disturbed more or less by stone quarries 

 and the like, doubtless some of them before Winchell began his study of 

 the falls. There remains clearly defined nearly all of the terrace which 

 occurred 10 to 15 feet above the limestone ledge, in several places, and 

 some part at least of another, to 5 feet above the limestone ledge, which 

 accompanied the former general^. Eiver shells occur in gravels along 

 the scarp between those two terraces. 



Within the gorge terraces occur in several places. On the left wall of 

 the gorge, at Meeker island, a narrow but characteristic block-covered 

 terrace begins at 55 feet below the top of the limestone ledge, 35 feet 

 above the normal river level, and descends with decreasing gradient 15 

 feet in 100 yards, and then for another 100 yards maintains about the 

 same elevation, 20 feet above the river. 



In Eiverside park, at the north end of Twenty-seventh avenue south, 

 on the right wall of the gorge, is to be seen the extreme end of a fall- 

 scarp and below it a rapidly expanding terrace. The present wall of the 

 gorge cuts obliquely across this scarp, so that all or nearly all of the orig- 

 inal rapids above the fallscarp had been cut away even before a stone 

 quarry Avas begun here. In the quarry 4 feet of hard crystalline lime- 

 stone strata and interlaminated shale of bed number 3 appears above the 

 14 feet of the regular upper limestone (bed numlier 2) and the lower 

 limestone. Since the crest of the fall appears to have been at the top of 

 the lower limestone, there would have been 18 feet descent in the rapids 

 above the fall. The old fallscarp is not well preserved in form, but its 

 top is seen 60 feet above the present river bed, and it has a gradient of 25 

 feet in the distance of 60 feet. Thence a descent of 20 feet in 200 paces 

 is followed by a gradient which parallels that of the present river for an- 

 other 100 paces. The terrace in this part becomes 100 feet wide and 

 then narrow again. Quarry dumps now conceal the narrow part for a 

 long distance, but I remember that it was continuous with the block- 

 covered strip which lies 15 to 20 feet above the river's normal level at 

 the Franklin Avenue bridge. 



The entire descent in falls and rapids at Eiverside Avas thus 60 feet, 



the river flowing thence 15 feet above the present normal level. The now 



remaining terrace displays on its edge next to the river a fine profile of 



the very irregularly eroded surface of Saint Peter sandstone, covered 10 



V — Bull. Geol. Soc. A.m., Vol. 10, 1007 



