364 The American Geologist. 
June, 1003. 
stream has swept across the flood i)lain carrying away sur- 
face soil and sand. These irrcgularitie-s are produced by cut- 
ting where the grade causes an increase in velocity ; where the 
velocity is decreased, deposits accumulate at flood time. 
When the ice '"goes out" in the spring, gorges form at places 
causing overflows. Then it is that the Platte is most erratic. 
Small sand dunes resulting from wind action occur near 
Fremont and Valley. The flood plain varies much in width, 
being ten miles wade at Fremont and about one mile wide be- 
low Ashland where the river strikes the resistant Coal Meas- 
ure beds. The inference, that ithe Platte by building up a stead- 
ily rising flood plain, has crowded the Elkhorn eastward and 
southward is cjuite generally drawn. 
Todd. Valley. — This valley, shut in on both sides by border- 
ing hills, opens at each end into the Platte valley of w'hich it 
seems to be a part. The altitude at the northern end is 1300 
to 1340 feet or 60 to 100 feet above the Platte; at the south- 
ern end, it is 1 120 to 1 140 feet or 20 to 40 feet above the Platte 
floor. The gradient averages about seven feet to the mile. 
The floor averaging 80 to 100 feet below the bordering high- 
lands, is for the greater part, level, not much dissected, and 
poorly drained, showing here and there low knoll-like eleva- 
tions with intervening wet-weather ponds. Except a few shal- 
low sloughs, the only irregularities of any consequence occur 
along Wahoo creek, and Sand creek. At each end the valley 
floor presents the appearance of a rounded terrace. 
The Highlands. — Except for the gradual ascent to the 
north and west, the highlands lie in the same general level. 
They are considerably elevated above the regions already de- 
scribed and show a hilly or older topography. Between the 
Platte and the Todd valley is a region three to six miles wide 
and over twenty miles long extending in a southeasterly direc- 
tion from near the high blufl:'s northeast of Cedar Bluffs to a 
point south of Yutan. This well drained hilly region, with a 
distinct divide, and occurring between the comparatively new 
lowland areas, has an important bearing in the subject under 
consideration. It seems to be a separated portion of the other 
highlands. 
Conclusion. — The surface indications cause one to l^elieve 
that the Platte river at one time flowed through Todd valley 
and that it has been diverted to its present position. 
