86 The American Geologist. August, i904. 
So long a time have the Missouri and its tributaries been 
at work, with a good rate of descent, eroding the mostly soft 
Cretaceous strata, in an unceasing task estimated by the pres- 
ent writer as seven to ten times longer than the postglacial pe- 
riod since the ice-sheet melted away from much of the area 
of South and North Dakota, from Minnesota, Wisconsin, and 
the moraine-inclosed part of all the northern states and of 
Canada. But through a still longer time, ever since the early 
Quaternary uplifting of the Plains from their low baselevel- 
ing, that is, probably 150.000 years, more or less, have most 
of the large streams outside the glaciated area been cutting 
down their valleys. 
What some of these streams, with their branches and ad- 
joining springs, have accomplished in sculpturing picturesque 
and almost indescribable chasms, gorges, and ravines, is the 
scenic and geologic wonder of the Plains, the widely famed 
"Bad Lands" {Mauvaiscs Torres), so named by the early 
French fur traders and trappers, because of the difficulties of 
traveling through or across these wildly and fantastically 
eroded tracts. This frequent phase of valley erosion under a 
somewhat arid climate is perhaps best displayed along the 
Little Missouri river, in the west part of North Dakota. It is 
well seen on a width of several miles in the vicinity of Medora, 
where the Northern Pacific railway crosses this valley, and al- 
so along all the course of this stream far to the south and 
north of the railway, to its union with the Missouri river. The 
weird efifects of the forms of erosion are further enhanced here 
by the bright red color of some of the beds, and in numerous 
places by jet black lignite seams. 
Twenty years ago- Theodore Roosevelt had a cattle ranch 
in this valley a few miles south of ]\Iedora, and ranged in his 
hunting excursions over all parts of these Bad Lands and the 
adjoining plains. His description of the valley sculpture, in 
"Hunting Trips of a Ranchman," may well close this paper, 
as follows : 
Our route lay througli the heart of the Bad Lands, but of course 
the country was not equally rough in 0II parts. There were tracts of 
v-arying size, each covered Avilh a tangled mass of chains and peaks, 
the buttcs in places reaching a height that would in the East entitle 
them I0 be called mountains. Every such tract was riven in. all direc- 
tions by deep chasms and narrow ravines, whose sides sometimes rolled 
