russell] LAVA STREAMS. 85 
probably below rather than above what an actual survey would show. 
The area covered by the lava stream is not less than 20 square miles, 
and may be twice that amount. 
The absence of angular fragmental material and of volcanic bombs, 
clots of lava, etc., on the surface of the congealed lava pool, other than 
fragments near the borders which have fallen from its inclosing walls, 
is evidence that the later stages of the eruption were not attended by 
explosions. The lava seems to have been poured out quietly and in 
immense volume, in much the same manner that a spring of water some- 
times comes to the surface and flows down a gently inclined channel. 
This is more than a casual simile, for the lava during the earlier stages 
of the eruption was certainly highly liquid, and was in reality a spring 
of molten rock which was caused to flow, as we have reason for believing, 
by pressure on a reservoir deep below the surface, which thus formed 
a stream that flowed far and spread wide on a nearly level surface. 
The outwelling of the molten rock was so quiet that not only were no 
volcanic bombs projected into the air, but no pasty clots or drops of 
liquid lava were spattered onto the bordering walls. 
The surface of the lava at the immediate summit of the material fill- 
ing the conduit is vesicular, and in part highly scoriaceous, but there 
is nothing approaching pumice or congealed frost to be seen. In fact, 
but little material of that nature was observed about the Cinder 
Buttes. The steam which rose with the lava seems to have escaped 
quietly before the magma became sufficiently cooled and stiffened to 
retain it until its pent-up energy resulted in explosions. That steam 
or gases were present in considerable quantity, however, is evident 
from the fact that nearly all the lava in sight is more or less vesicular 
and in many instances highly scoriaceous. 
The northwest lava stream, and the same is in general true of all 
the recent lava flows about the Cinder Buttes, came to rest and finally 
hardened with such a low surface slope that from a little distance no 
eye can distinguish it from a perfect plain. For the first mile or so 
below the fountain-like source from which it came there is, it is true, 
a perceptible northward slope, but it is so gentle that a casual observer 
would scarcely note its presence. 
But a few rods south of the congealed lava pool just described and 
separated from it by a fragment of a tuff cone, a pc 'ion of which was 
undermined by the lava flowing past its base and broken away after 
the manner of a landslide, another and larger lava stream came to the 
surface and flowed southward. This southwest lava flow had its source 
in two lava pools, but the molten rock discharged by them soon united 
so as to form one stream, which, at a distance of perhaps a mile, was 
joined by another and still larger river of lava having its source about 
a mile to the west of the base of the highest of the Cinder Buttes, and 
the united flow continued southward for a distance of between 25 and 
