Editorial Comment. 321 
On the opposite side of the Black hills and a little further 
south is In van kara (pronounced by the Indians Heeng-ya- 
kaga). This was also examined by the writer, who gave the 
appended illustration.* This rock also is phonolyte. Newton, 
however, states that it is trachitic, with crystals of sanidine 
sparsely disseminated. The central mass is almost entirely 
surrounded by a rim of rock similar to that of the central mass. 
The sedimentary beds of the Carboniferous strata lie at steep 
angles against the flanks of the rim, but do not rise more than 
500 feet above the plain. "The shape of the summit which at 
a distance has the aspect of a small saucer lying on a larger 
one, both inverted, is caused by the central mass rising above 
the rim or ridge by which it is nearly surrounded. The only 
opening in this rim is toward the north 10" east, where it is en- 
tirely wanting. This ridge is about three-fourths of a mile 
distant from the central mass. Its main axis runs about north 
and south. The intervening space is occupied by a dark val- 
ley, shaded with Norway pines. It is very difficult, and in 
many cases impossible, to pass from the ridge to the centre 
across this gorge, the rock rising sheer up on nearly all sides 
about the central mass." The main mass has not a distinct 
basaltic structure, but it is cut by jointage planes that are in 
three systems, viz : one series runs about east and west, the in- 
dividual planes being about ten inches apart, or closer; an- 
other series runs northeast and southwest, the planes being 
four feet apart and having their tops tipped toward the south- 
Hceng-ya-kRga peak. A sketch made by N. H. Winch ell in August, 1874. 
• Report of a rcconnissance of the Black Hills of Dakota made in the sum- 
mer of 187+. bv William LiJDLOW. Appendix PP. of the Annual Report of 
the Chief of Engineers for 1875, p. 37. 
