CHARACTERISTICS OF THE PLAINS AREA. 279 
Near the meridian of 117°, and just north of Milk River, begins an 
area of sparse vegetation, which extends southeast across Milk, Missouri, 
Musselshell, and Yellowstone Rivers, and terminates in the western part 
of Dakota, north of the Black Hills. Its boundaries are very ill-de- 
fined, as it grades off on all sides into the ordinary grass land of the 
prairies. Where it crosses the boundary line it is not far from 75 miles 
iu width. Its western limit crosses the Missouri not many miles below 
Fort Benton, runs around the Judith Mountains at a distance from them 
of not far from 10 miles, crosses the Musselshell in longitude 110°, and 
thence bears generally southeast, keeping at a distance of a few miles 
from the eastern base of the Yellowstone and Big Horn Ranges. Its 
greatest southerly extension is reached between the Big Horn Range 
and the Black Hills. Thence passing northeast by the Black Hills, its 
line, now its eastern boundary, runs north in the longitude of the eastern 
base of the Black Hills, embracing the Bad Lands of the Little Missouri, 
the Powder, and Lower Yellowstone Rivers. Crossing the latter stream, 
it runs generally northwest -to the point first mentioned. North of the 
Yellowstone, this region is characterized mainly by the sparsity of all 
vegetable growth, the grass is scanty and short, and there is much 
cactus. South of the Yellowstone, on the lower waters of that stream, 
the Powder, and Little Missouri, are Bad Lands, where the surface is much 
broken by minor typographical features, caused by the rapid erosion of 
soft strata. There is but little vegetation, with great areas of bare, 
powdery, clay soil. Higher up, on and between these streams, the preva- 
lent growth is sage. 
What has been said regarding the vegetation of the second and third 
prairie levels is equally true concerning the coteaus of the Minnesota 
and Dakota. While forming parts of these prairie levels, they are in 
fact plateaus of no great elevation, being 1,500 to 2,000 feet high, and 
well marked by bluffs everywhere, except on the north. They have 
a rough, undulating surface, gravelly or rocky soil, containing many 
" sinks," but are not well watered.. The luxuriance of the grasses varies 
very much with the locality, but is nowhere too sparse to burn with the 
utmost freedom. 
Within the United States the general character of the grasses may 
be thus briefly expressed : 
In Central Nebraska and Kansas, Western Indian Territory, and Cen- 
tral Texas, which is the belt lying just west of the western border of 
timber, the grasses are high and luxuriant, as should be expected, on 
account of the comparative moisture of the climate. Westward, as the 
aridity becomes greater, the grasses become shorter and sparser, and 
this progression continues until we near the Rocky Mountains, where 
their influence in rendering the climate moister is shown in the increased 
luxuriance of the grasses. 
In all this wide expanse of plains south of the Black Hills the area 
which cannot be easily burned over is very small. The* Bad Lands be- 
