322 The American Geologist. '^^^'- i^^^- 
east about io° ; while a third runs perpendicular to the last and 
has its tops inclined toward the northeast about io°. These 
larger divisions of the rock cause, on being weathered, the 
columnar structure seen all about the sides of the central mass. 
There is, besides, on the western side of the central mass, a 
fourth system of joints that slope downward toward the west 
at an angle of about 45°, which gives the whole mass at that 
point the appearance of being a heavy bedded upheaved sedi- 
mentary rock. In general, the central mass has a structure that 
implies greater pressure on the western side with a tendency 
at the top to curvature toward the east. It may be due to a 
confused or interrupted basaltic jointage produced in cooling 
gradually, and while }et in slow upward movement. The top 
•of this central mass therefore may have presented originally a 
vertical or overhanging face on its eastern side. The bight of 
Heeng-ya-kaga is about the same as Bear butte. 
Bogoslof island, in the Aleutian series, is a volcanic cone 
or peak which apparently belongs to the same category. Two 
views of this are presented in plate xxi. These are taken 
from Science, March 7, 1884, where is an account of this island 
and its changes within historic time, by professor J. E. Hilgard, 
superintendent of the United States coast and geodetic sur- 
vey, written by George Davidson. The upper view represents 
it in 1768 and 1769. In 1778 captain Cook saw it, and says 
that it was an elevated rock which appeared like a tower, rising 
above the surface of the ocean. He judged of its steepness 
.below the surface of the sea by the fact that the waves, which 
were running high, broke nowhere but against its sides. This 
island seems to have been destroyed, perhaps by the waves, and 
to have risen again later at a slightly different place, one au- 
thority saying that it rose anew from the sea in the early part 
of May, 1796. The bight of the original rock is not certainly 
known, but has been given at 400 feet, 600 feet and at 840 feet, 
the last by a Russian navigator. Professor Davidson quotes 
the following from a work by Veniaminoff : 
"Before the island appeared above the sea there had been witnessed, 
for a long time in that spot, a column of smoke- On the 8th of May. 
after a strong subterranean noise, with the wind fresh from the north- 
west, the new, small black islet became visible through the fog ; and 
from the summit great flames shot forth. At the same time there was 
a great earthquake in the mountains on the northwest part of Umnak 
