42 TJte American Geologist. jan. isoo. 
ter are of red Triassic sandstone, averaging 400 to 6U0 feet in 
the steeper part, whilst from the top of the lapilli-covered hills 
sloping gradually down into the steep throat of the crater, the 
hight was over a thousand feet. The crater may thus be said 
to be about one thousand feet deep. The bottom of the crat- 
er is oval and comparativel}'^ flat, dipping, however some five 
or more degrees to the south, that is, toward the side where the 
lava seems to have broken through and poured out. The diam- 
eter of the bottom is between 200 and SOOyards, the surface is 
covered with debris and sage-brush, doubtless overlying a sol- 
id plug of congealed lava. The width of the crater at its steep- 
er portion, is between 500 and 800 yards. The sides are quite 
steep, having an inclination of from 45 to 75 degrees, and 
would be rather difficult to climb up or down. I did not make 
the attempt from lack of time. There is no natural exit or en- 
trance to the crater. It is a complete cup. The red sandstone 
strata forming the throat dipped inwards at an angle of 
from 30 to 40 degrees, and appeared to converge toward the 
centre of the crater. Time only allowed me to make some 
rapid sketches and hurried observations, but from what I saw 
I think the following may be the history of this undoubtedly 
true crater and volcanic vent. 
At some time, probably within the human period, eruptive 
forces found a vent at this point, and explosions of steam blew 
out a crater hole in the upper Carboniferous and Triassic 
strata. That the action was explosive. I judge from the great 
quantities of lapilli and comminuted fragments of shale and 
sandstone covering the surrounding the hills. The steam de- 
scending as water worked up some of the lapilli into a strati- 
fied breccia around the rim of the crater. When the explo- 
sive energies, that had filled the sky with steam and lapilli, de- 
scending in showers upon the surrounding hills, had subsided, 
a volume of lava arose in the throat of the crater, and poured 
out over the lip on the south side, partly breaking through the 
crust of breccia, and tilting it up as it passed through it. From 
the lip of the crater it poured rapidly down the steep face 
of the hill, and thence down the narrow ravine into the open 
valley, where it spread out as a cake of lava over the meadows 
and on to the river wdiich it may have temporarily dammed 
back. The course of the lava was finally checked b}' coming 
against the abrupt cliff forming the south bank of the Eagle, 
