36 SNAKE RIVER PLAINS OF IDAHO. [bull. 199. 
is only in the ravines on the northern slope, where snow accumulates 
most deeply and remains longest, that conditions are favorable to the 
growth of young trees. The vegetation, if studied critically, would 
evidently furnish a delicate index to the climatic conditions. 
On reaching the summit of Big Butte on a clear day there is a far- 
reaching view in all directions, and much of the history of the Snake 
River Plains may be easily read in the splendid panorama. 
In attempting to understand the features of a landscape when beheld 
from an elevated station, it is necessary to have in mind the scale on 
which the relief map, for such it appears, which is spread before one, 
is constructed. In arid regions, in spite of the haze usually present, 
distances are deceptive. Objects leagues distant seem only miles away. 
The mountains to the east are f ull} T 50 miles distant, and the nearest 
peaks to the west are from 30 to 40 miles away; to the southwest and 
northeast the flat plain extends indefinitely, and no bordering shore is 
in sight. In spite of their remoteness, the Lost River Mountains to 
the west are clearly and even sharply defined. The upward sweep of 
alluvial fans can be easily traced to Avhere they narrow at the mouths 
of strongly cut gorges. Above their summits are the outlines of bare 
crags, where angular rocks form bold convex curves, which replace 
the concave curves due to stream deposition on the lower slopes. 
Still higher is a dark band of forest which encircles the mountain like 
a shadowy wreath. Far above the timber line arc bare serrate peaks, 
all of them light gray and suggesting the presence of limestone or 
quartzite, except the highest pinnacles of all, which gleam silver white. 
A recent storm, which brought light showers to the plains, covered the 
higher mountains w T ith snow. Roads on the plain appear as line lines 
radiating from the spring at the northern base of the mountain. Each 
curve in the yellow line leading west can be clearly followed to Arco, 
14: miles distant, where clumps of bushes and a few houses tell of the 
presence of water. Other clumps of hushes and here and there a field 
of alfalfa, a rectangular patch of green on the vast gray expanse, 
reveal the curves of Big Lost River as it flows through the plain, 
bends northward, and in winter maintains its existence for about 50 
miles to where it spreads out in a small lake. To the northeast, and 
seemingly close at hand, although 15 and 20 miles distant, Middle and 
East buttes rise abruptly. The nearer butte is black, its sloping 
surface is inclined to the southeast, in conformity with the dip of the 
hard rock layers of which it is composed. The western border is 
abrupt at the summit, but below it has much more gently inclined 
lines, due to talus slopes. East Butte is white, rises sharply on all 
sides, is without conspicuous talus slopes, and terminates above in two 
sharp, angular peaks, between which there is a smooth, saddle-shaped 
depression, suggestive of a broken crater. A view of this remarkable 
steptoe, taken from near Middle Butte, is presented in PL V. 
