400 Scientific Intelligence. 
1857, but have as yet afforded no Gasteropods; that all the for- 
mations are conformable to one another from the as to 
the Primordial. The volcanic peaks occur over the part of the 
Hills north of the parallel of 44° 10’, without any linear arrange- 
ment or special eto in distribution, On the northeast margin 
of the Hills is Bear Butte; on the northwest side, in Red Valley, 
and another unnamed ; on the Belle Fourche, Mato Tepee or Bear 
Lodge, the three Little <The Buttes ; within the area, Custer, 
Terry (the crowning peak of the gr oup), Crow Peaks and Black 
Butte, besides others less conspicuous. The rock of the cones is 
mostly sanidin trachytes, partly rhyolitic. No evidence of over- 
flo as found, with a single small exception, as if there had 
been singh an extrusion of densely viscid materia 
The peaks are cones, with sometimes regular craters, and vary 
in height above the valley at their base, from 300 to 180u feet. 
Custer Peak is 675 feet above its base and 6,950 Se the sea. 
Bear Butte is 1,200 feet above its base and only 4,570 above the 
sea, being about six miles from the edge of the foot-hills, Inyan 
Kara is 1,300 feet above the bed of the creek of the same name, 
oe : ,600 feet above the sea 
ar Lodge “isa great rectangular obelisk of neo porphyritic 
sian with a columnar structure, giving it a vertically 
striated appearance, rising 625 feet almost per en dicolaely from 
its base. Its summit is so entirely inaccessible that the energetic 
explorer, to whom the ascent of an ordinarily difficult crag is but 
a te pastime, as he stood at its base could only look ‘upward 
in despair of ‘ever planting his feet on the top.” The height 
oes the Belle Fourche is 1,126 feet, and its height above “i 
sea approximately 5,260 feet; the width at bottom is 796 fee 
and at top 376 feet. In outline it is like the now un saratan 
Washington Monument. The columns of the columnar trachyte 
m 
comparison w with any known basaltic phenomena 
Another remarkable feature of this locality is i undisturbed 
condition of the surrounding Potsdam sandstone; at a distance of 
but 50 to 75 feet from the base no evidence of any tilting —_ 
be detected, but the sandstone Jis “converted for some distanc 
into a compact white quartzite.” 
The Little Missouri Buttes have a height of but 400 to 500 feet. 
They stand on the Dakota sandstone; but this floor-rock “ could 
not be ascertained to exhibit any disturbance or change of struct- 
ure due to the proximity of the igneous matter. The rock is green- 
ish-gray trachyte, and there is also at the base, in one or two local- 
ities, (what is not mentioned as occurring about the other peaks) 
an ape ee. od light and cellular rock, ‘yellowish in color, very 
like a volcanic tufa or rhyolite breccia, including fragments of 
both steers and rhyolite. 
