108 The American Geologist. August, 1894 
of a fine-grained, gray muscovite-granite, homogeneous 
throughout, and appears to be, as far as can be judged from 
its present features, an eruptive plutonic body, a true lacco- 
lite. The only variation from the even fineness of crystalliza- 
tion is the presence of crystals of tourmaline porphyritically 
developed, and intergrown with other minerals. These crys- 
tals are usually an inch and a half in length. They do not 
Occur at a distance of more than three feet down from the 
surface of the granite, as I was able to observe in the exten- 
sive quarries now being worked upon the mountain. 
Since tourmaline is a mineral whose presence in granite 
usually denotes a contact with other rock, the presence here 
of crystals of tourmaline near the surface, and nowhere else. 
is evidence in favor of two things: (1) That Stone mountain 
has been covered with beds of rock, probably with gneiss like 
that which surrounds it. The noncrystalline nature of the 
stone itself bears out this theory, (2) That, although the 
cover lias been removed, little of the granite has been eroded. 
Indeed, I think it probable that the shape of the mass has 
been but little changed since the granite cooled. Hence it 
may be referred to as a stripped laccolitic mass. The moun- 
tain reaches two and a half miles in its long diameter, and 
nearly a mile in its shorter one. The slope of the sides varies 
from 30° on its southeast side to as high as 70° on the north- 
east. A granite mass similar to Stone mountain, but much 
smaller, comes up through the plain twelve miles to the south- 
east. 
The difference in structure between Kenesaw and Stone 
mountains is roughly shown in the accompanying cross-sec- 
tions (figures 3 and 4, plate iv). 
EDITOPxIAL COMMENT. 
The Columbian Exposition. 
Sovu special State exhibits of the crystalline rocks. 
< >!' the New England State-. Massachusetts excelled, although 
Connecticut; and Maine also had suites of dressed granite 
cubes four inches on the edge, the labels of the latter express- 
