50 GEOLOGY OF SW. IDAHO AND SE. OREGON. [bull. 217. 
scarp, but is by no means certainly of that nature. The only unques- 
tionable evidence of a break in the rocks on which the crater stands 
is furnished by a row of about 12 driblet cones, situated in a line 
extending west from the principal center of eruption and up the slope 
of the hill at right angles to the faint escarpment referred to above. 
The portion of the break on which the driblet cones are located, 
situated at a distance of about 1,000 feet from the center of the main 
crater, shows no evidence of a differential movement of its walls. 
There is then but slight evidence of a shattering or faulting of the 
country rock preceding or following the birth of the volcano. 
The portion of the original pile of cinder and lapilli remaining at 
Crater No. 1 is highest on the south side of the crater, where it rises 
about 100 feet above its outer base and somewhat more above the irreg- 
ular pit it partially inclosed. The cone has lost much of its symmetry, 
owing to the falling of its inner surface, and on the south side of the 
crater presents a fairly good section of outward-dipping layers of lapilli 
and of compact reddish lava. The compact layers referred to are 
among the more interesting features of the section, and while having 
the appearance of lava flows which descended the outer slope of the 
lapilli and scoria cones when it was but partially completed, are in 
reality due to the flowing together and cooling in one mass of man}- 
splashes of liquid lava. This mode of origin of the dense compact layer 
is shown by it containing angular fragments of lapilli and by small, 
isolated, lenticular masses of the same nature completely embedded 
in lapilli, with which it forms a complete gradation. More than this, 
the surrounding surface of rhyolite, adjacent to the base of the cinder 
and lapilli cone, where not concealed beneath lava flows, and to a 
distance of about 800 feet, is thickly strewn with reddish clots of lava, 
which were liquid when they fell and in general ran together, so as to 
form a tide-like sheathing to the surface. This material spattered 
out of the crater and falling well beyond, its base is of the same char- 
acter as the layer of dense lava built into its wall and covered by 
subsequent showers of lapilli. The preservation of the rough, angu- 
lar pavement, composed of congealed splashes of lava about the crater, 
which fell in a liquid condition, thus serves to explain the history of at 
least certain compact layers in the walls of the cinder cone, the most 
noticeable of which has a thickness of between 10 and 20 feet. Simi- 
lar compact, usually reddish, layers of lava in cinder cones have been 
observed at the Cinder Buttes and elsewhere, as already explained, 
and are evidently a common feature of the walls of cinder and lapilli 
craters built by volcanoes which discharged highly liquid lava. 
After a small cinder and lapilli crater had been built by the volcano 
under discussion, it is evident from the records still remaining that 
liquid lava rose within it and breached its wall, both on its west and 
southeast borders. The lava which escaped westward was small in 
amount and now forms a pool-like sheet of black pahoehoe about 600 feet 
