88 GEOLOGICAL RECONNOISSANCE 
wet it exhibited, however, the hues and appearance which it would pos- 
sess, if polished, and gave one a better idea of its tints and the variegated 
aspect of its surface, than could be obtained from an inspection of the rock 
in its native bed. The coloring matter is due to oxide of iron, irregularly 
distributed in the mass, and in that high state of oxidation and allotropic 
condition in which it is but little disposed to unite with nitric acid, even at 
a boiling temperature. At a future period, we intend submitting a chemi- 
cal analysis of this marble limestone, which will give the per centage of 
metallic oxide that enters as a coloring principle into the composition of 
this rock, which may be regarded as one of the most valuable mineral pro- 
ductions of this part of Arkansas. 
It had been supposed, that oxide of manganese entered into the compo- 
sition of this material, but the specimen submitted to a qualitative chemi- 
cal examination for this metallic oxide, gave no indication of its presence, 
although the test applied is so extremely delicate, that it will distinctly 
indicate even the minute trace of manganese found i in some specimens of 
white Carrara marble. 
The conspicuous range of hills, lying partly in- Carroll and partly i in 
Newton county, whose northern terminus bounds the Marshall prairie, on 
the south, is composed of two flanking peaks, and a central flat-topped 
ridge. 
The most southerly of these conical peaks is known ts the name of-the 
“Pilot mountain ;’’ the northern one is called the “ Stack mountain ;” while 
the middle ridge has received the name of the “ Boat mountain,” from its 
fancied resemblance to a boat, rising out of the adjacent prairie, like some 
gigantic water-craft resting on the ocean. 
The view represented by wood-cut No. 12, was taken on the edge of the 
Marshall prairie, near the corner of the three counties of Carroll, Newton, 
and Searcy, and exhibits the Boat mountain in the background, flanked 
on the left by Pilot mountain, and on the right by the Stack mountain. 
The indistinct terrace seen towards the summit of the Boat mountain 
is formed by cliffs of conglomerate, partly concealed by trees and vegeta- 
tion, and forms ue highest bench of prominent sandstone in this moun- 
tain. 
The Boat mountain rises to the height of 844 feet above Marshall’s 
prairie, at the foot of the principal ascent, and 1,244 feet above our en- 
campment of the 23d of June, on Marshall’s creek. By computation, its 
summit must be about 1,527 feet above Little Red river, at Clinton. 
Black bituminous shale is in great force at the base of the mountain, 
extending 70 fect up the slope, resting on light-gray limestone, with segre- 
gations or intercalations of chert.. 
