GREGORY.] MARS HILL. 135 
these rocks as Devonian sandstone, and states that they are of the same 
age as the red sandstones of Mapleton. 
Rock structure. — With the exception of the igneous rock described 
in another chapter, Mars Hill is composed of a conglomerate which in 
places becomes quite fine grained. The structure of the mountain and 
the relation between the different rock formations are shown by the 
section, fig. 7. 
The section is made straight east from the Boynton schoolhouse to 
the top of the mountain. 
Near the schoolhouse occur the sandy, calcareous slates of this region; 
nearer the hill is a layer of very fine sandstone, about 50 feet wide, 
which is composed of quartz grains with some feldspars set in a calcite 
cement. Extending from this sandstone to the base of the hill, a dis- 
tance of about half^a mile, is a whitish to blue brecciated limestone, 
which is closety folded and faulted and cut by cleavage planes that 
are now filled by secondary calcite. The limestone is not uniformly 
calcareous, but contains sandy streaks, especially near the hill. 
Fig. 7.— Section at Mars Hill. 
The lower slope of the hill is of medium-grained breccia composed 
of fragments of sandy slates and sandstones, which soon passes into a 
very coarse, rough breccia composed of large fragments of sandy and 
argillaceous slates, together with fragments of arkose and other vari- 
eties of sandstone and rarely a fragment of an igneous pebble. The 
fragments are subangular. The whole mass is slated and sheared and 
has all bedding lines destroyed. 
From halfway up the mountain to the top the slate fragments, which 
are so abundant below, disappear as the predominant element in the 
rock, and are replaced by pebbles of sandstone, arkose, quart/it e, 
hardened slates, and white quartz. The pebbles are rounded and vary 
from those that are fine-grained to those 4 inches and more in diameter. 
The cementing material is very firm, as is shown by the fact that the 
cleavages break through the pebbles. 
The sandstones and conglomerates exposed on other parts of Mars 
Hill are much like those in this section, and show variation in fineness 
and amount of induration. 
