156 LEWIS G. WESTGATE AND E. B. BRANSON 
Plain No. 1.—After the completion of No. 2, the streams again 
deepened their valleys and developed widely over the region a 
series of plains at a lower level. Along the Beaver north from 
Hailey a flat was formed 8 to ro miles in width, sloping with the 
stream and toward the stream from either side. Near the Beaver 
the remnants now stand 200 feet above the stream. Above the 
lower Beaver cafion, a little up stream from Hailey, this plain is 
not shown; nor is it recognized along the Sweetwater. 
The valley divide which crosses north of Twin Creek from the 
main range foothills to Sheep Mountain, is a remnant of No. 2, 
but from here north the divides between the streams which cross 
the valley belong to No. 1. On the Little Popo Agie-Willow 
Creek divide the elevation is 5,575 feet, north of Willow Creek 
5,450 feet, and south of Lander 5,480 feet. The remnants of this 
plain slope from either side toward the axis of the longitudinal 
valley, indicating that the stream which controlled its formation 
was a longitudinal stream flowing northwest toward Lander, and 
that the valley was not drained as it is today, by transverse streams. 
North from Lander, between the Popo-Agie and its north fork, 
a terrace runs far out into the valley and at Milford stands at 
5,800 feet. North from this point a series of terraces occurs, 
below the Table Mountain levels, the highest of which are referred 
to level No. 1. These terraces stand at 5,730 feet between North 
Fork and Mill Creek, and at 5,940 feet near the road, north of the 
North Fork of Little Wind River. The levels rise toward the north- 
west, along the Wind River, and also toward the mountains. 
The cutting of No. 1 was the inauguration of a period of terrace 
cutting which has continued to the present. New plains have been 
made by the swinging and deepening streams at successive lower 
levels, but since this terrace period has been different in the differ- 
ent stream basins, and since in any one basin the terraces run into 
each other, it was found impossible, in the absence of topographic 
maps, to study it in any detail. Between the North Fork of the 
Big Popo-Agie and the Little Wind River these lower terraces often 
carry large bowlders, up to 3 feet and over in diameter, which seem 
to have been derived from the erosion of the coarse gravels on 
plain No. 2, since largely destroyed. 
