80 SNAKE RIVER PLAINS OF IDAHO. [bull. 199. 
It mav be noted that no foreign or included rocks, such as fragments 
of granite, quartzite, etc., or pebbles derived from older terranes, 
except a single fragment of obsidian, were observed about the Cinder 
Bnttes. The buttes are built entirely of basaltic lava. 
PARASITIC CONES. 
The eruptions to which the Cinder Buttes are due were character- 
ized in their earlier stages by explosive violence, during which com- 
paratively small cones of lapilli, scoria, bombs, etc, were formed, and 
later by an outpouring of immense volumes of liquid lava. When the 
lava ceased to flow, the portions remaining in the conduits through 
which it rose cooled and hardened, and the lives of the volcanoes ceased 
without a renewal of the steam explosions which accompanied their 
birth. In one instance, however, there was a partial exception to this 
rule. 
About 2 miles northwest of the highest of the Cinder Buttes, and 
on the surface of a bare, corrugated lava stream near where it came 
to the surface, there is a row of seven steep-sided and remarkably regu- 
lar cones, composed principally of rough ball- like masses of highly 
vesicular or scoriaceous lava (PI. XI, A). These balls or imperfectly 
formed bombs are usually from 8 to 14 inches in diameter, and when 
they fell were sufficiently plastic to adhere one to another, so as to 
form what at first were nearly vertical walls. The sides of these 
cones near their summits now have slopes of from 50 to 56 degrees, 
but decrease below to 34 degrees or less, owing to the accumulations 
of small quantities of fragmental material about them. Their steep, 
upper slopes are angular and rough, but the lower slopes, when seen 
in profile, present curves such as are characteristic of lapilli cones. 
Not only were the spherical masses plastic when they fell, but in one 
observed instance a splash of lava tossed out and falling on the exterior 
of a cone ran down several feet before cooling. In addition to the pasty 
and liquid material ejected, there is a minor quantity of angular frag- 
ments, but these were not thrown far, and the surface of the lava 
stream on which the cones stand is entirely bare at a distance of but a 
few score feet from their bases. The cones are symmetrical and the 
distribution of the lapilli about them shows no evidence of a strong 
wind blowing at the time they were formed. 
The craters, with one exception, range in height from about 40 to 
<><> feet. The exception is furnished by the most westerly in the 
series, which is much lower than its companions and does not rise 
more than 15 feet above the surface of the adjacent portion of the 
lava stream on which it stands. The trend of the line of cones is about 
southeast, or in the same general direction as that of the belt of vol- 
canoes with which they are associated. The cones are located at quite 
