40 The American Geologist- jan. isso. 
large boulders, of a black vesicular basalt or scoria. The cavi- 
ties or vesicles in this scoria, are sometimes several inches in 
diameter, and are frequently lined with white zeolitic crystals. 
The railway depot at Antonito is built of this black scoria. 
The ranchmen of the park told me there was a crater-like de- 
pression in the mountain. The cone is in full view from the 
railroad station at Antonito. 
The Dotsero Volcano. 
Whilst spending a few days at Glenwood Springs, Garfield 
county, I heard accounts of a crater and very recent-looking 
flow of lava being near Dotsero station, not far from the junc- 
tion of the Grand and Eagle rivers, about sixteen miles east 
of Glenwood on the Denver and Rio Grande railroad. 
I started by a freight train for the locality. Our course for 
some twelve or fourteen miles lay through a canon in the Cot- 
ton-wood range. This range is formed of Cambrian, Silurian 
and Carboniferous strata, folded up in a faulted arch over a 
granite axis. 
At Glenwood are the noted Hot Springs, which issue proba- 
blj" from deep-seated fissures, formed at a point near the com- 
mencement of the range and the entrance of the canon, where 
the Triassic and upper Caxboniferous strata are bent into a 
sharp synclinal fold. At this point of extreme compression? 
fissures were probably formed, which descended to sufficient 
depths to give rise to the heated and chemical waters of these 
wonderful springs. Hot springs also occur in much the same 
relation on the opposite side of the range. 
As we emerge from the Cotton-wood canon to the east, the 
country becomes more open. Upon the Paleozoic rocks, rests 
the Mesozoic series. The hills on either side of the Eagle, con- 
sist of the soft gypsiferous beds of the upper Carboniferous 
and above them in due order the red and variegated strata of 
the Triassic and Jurassic series. 
The valley of the Eagle between the hills is from one to two 
miles in width. About a mile from Dotsero station the river 
hugs the south edge of the steep face of the hills. Just at 
this point a very black looking rock covers the meadow of the 
valley, spreading out like a large pancake, over an area of about 
a square mile. The edge of the cake ends abrubtly at the 
river side near the base of the cliff forming the south bank of 
the stream, the river separating it from the cliff beyond. As 
