284 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 
The Bighorn Range, which surrounds the basin of the Bighorn on 
three sides, is described as being heavily timbered, while the country 
about its base is exceptionally line for pasturage purposes, the grasses 
being very high and luxuriant. 
Next we turn to that great area marked on our maps as the "Great 
American Desert," the Green River Basin. This district, occupying 
about 11,000 square miles, is limited sharply on the south by the Uinta 
Mountains. The southern part of the western boundary is ill-defined, 
being simply a broad, meridional swell in the surface, separating the 
basin from the valley of the Bear River, a large tributary to Great Salt 
Lake. Following this divide northward, however, it is seen to develop 
into high ridges, which, still farther north, have weathered into mount- 
ains, the Wyoming Range. The basin extends northward almost to a 
point, abutting against the Gros Ventre and Wind River Ranges, the 
latter of which tonus a well defined eastern boundary as far as its cud 
near South Pass. Beyond this the eastern boundary is as poorly de- 
fined as the opposite western boundary, the land rising by almost imper- 
ceptible grades from the basin to the plateaus of the continental water- 
shed, above mentioned. 
The northern part of this great area is slightly broken by spurs from 
the mountains and by fragments of mesas, which have been spared by 
the erosive agencies. The central and by far the larger part of the 
basin is unbroken, save by long, gentle undulations, like those of the 
plains and by the bluffs, which limit the valleys of the few streams 
which venture into this arid expanse. In its southern portion, on the 
other hand, the conditions which prevail in the plateau province proper 
begin to assert themselves. River benches and bluffs develop into cliffs, 
and valleys change to canons. 
A corresponding gradation in the character of the vegetation is also 
plainly traceable. While the southern and lower parts of the basin are 
as arid as almost any part of the North American Continent, the north- 
ern and higher parts are well grassed and contain comparatively little 
sage and no greasewood. The greater part of the basin, however, is 
of too desert a character to be burned over economically. Those parts 
where the reverse is the case may be summed up as follows : 
The country between the Big Sandy River and the Wind River Mount- 
ains; indeed, all that near the southwestern base of this range, the 
southern part of the basin, extending as far south as Lead Creek, with 
the western rim as far as Fontenelle Creek, are sufficiently well grassed 
to burn with tolerable freedom. 
The soil of the basin varies extremely in different parts. Near the 
mountains it is, in all cases, naturally gravelly, coarse or fine according 
to the distance from their base. At the foot of the Wind River Range, 
about the debouchure of the several branches of New Fork of the 
Green, glaciers have in former time brought down immense quantities of 
boulders, gravel and the like, which now cover great areas. Farther 
