rtjssell.] BIG, MIDDLE, AND EAST BUTTES. 87 
Still farther to the northeast, and, as one is surprised to learn on 
referring to a map, 46 miles away, the outlines of Market Lake craters 
are clearly visible. Their characteristic conical forms, with flat sum- 
mits, leave no doubt that they are extinct volcanoes. From personal 
examination 1 know they are tuff cones with craters in their tops. 
When the eye has become adjusted to the novel conditions it per- 
ceives that the vast plain is not absolutely flat and featureless, and as 
evening approaches and a strong side light causes even small eleva- 
tions to cast shadows, many cone-shaped prominences rise from the 
previously flat surface. That these are extinct volcanoes is clearly 
shown by an example, only 3 or 4 miles distant to the southeast, from 
which a black stream of lava with a bare, rough surface, evidently of 
recent date, extends northward, and expands into a belt a mile or 
more wide before terminating. This recent addition to the rocks of 
the plain resembles a great withered and blackened leaf, with its petiole 
still attached, laid on the flat surface. Another black lava stream, 
starting from an elevation a few miles to the eastward, also flowed 
northward and expanded into a leaf -like form several square miles in 
area. These two recent lava streams indicate that the plain of which 
they form a part has not been produced by a single vast outpouring of 
molten rock, but is in reality highly compound and consists of many 
widely expanded and overlapping lava sheets. A small elevation, the 
summit of a low cone with an immensely expanded base, occurs about 
8 miles to the south. It is similar to those from which lava was 
recently poured out, but is much older. The lava has evidently flowed 
away from a small opening in all directions so as to form a cone, with 
a diameter at the base of certainly 8, and probably as much as 10 miles. 
When this old volcano is seen in profile from the surface of the 
surrounding plain it presents the appearance of another similar cone, 
shown on PL XVIII, about 15 miles to the west of Big Butte. The 
cone just referred to, together with two companions, is also in sight 
from the summit of Big Butte, and still others of similar shape, all 
broad, low cones, usually with flat summits, may likewise be distin- 
guished. Most of the small volcanoes are situated south of an east- 
west line drawn through Big Butte, but to the northeast there is 
one prominent brown crag only a short distance north of the wagon 
road leading to Blackfoot. Still farther north, and beyond the 
straight line formed by the railroad now in process of construction, 
are two other low mounds, which from near inspection I found to be 
remnants of basaltic craters. Far to the south, and nearly lost in the 
dim distance, are still other elevations, which have the same topo- 
graphic forms as those nearer to hand, and which I believe are also 
old craters, although as } r et unvisited and undescribed. To the west, 
close to the far more prominent mountains, yellow with withered 
grass, are the Cinder Buttes, among which a score or more volcanic 
