J. 8. Diller—Eruption in Northern California. 45 
From the different extent to which the various layers of this 
glassy rock have been inflated by the expansion of gas near 
the surface of the flow.it is evident that there was a difference 
in the amount of vapors previously absorbed by these layers. 
And from the part which superheated water has undoubtedly 
played in the development of lithophysze and the larger, po- 
rous spherulites, and from the aqueo-igneous conditions deemed 
necessary for the production of the granophyre groups of quartz 
and feldspar, it seems highly probable that the differences in 
consistency and in the phases of crystallization producing the lam- 
ination of this rock were directly due to the amount of vapors ab- 
sorbed in the various layers of the lava and to their mineralizing 
influence. 
Art. V.—The latest Volcanic Hruption in Northern California 
and wuts peculiar Lava; by J. S. DILLER. 
In making a geological survey of the northern terminus of the 
Sierra Nevada range in California, under the direction of Cap- 
tain C. H. Dutton, to determine its relations to the volcanic phe- 
nomena farther northward, several opportunities were afforded 
to visit and study the phenomena resulting from the latest vol- 
canic outburst in that region. It occurred at a place which is 
now pretty well known in that part of the world as “The 
Cinder Cone” near Snag Lake, about ten miles northeast of 
Lassen Peak, in Northern California. The newness of all the 
phenomena connected with this volcanic eruption is so striking 
when compared with those of other outbursts in the same 
vicinity that many of the country people and tourists are led 
annually to visit the locality, but until recently it has not been, 
carefully investigated. 
The Cinder Cone is a remarkably regular truneated cone ris- 
ing about six hundred and twenty feet above the lowest portion 
of its base, and is composed almost exclusively of small scoria 
and lapilli. Its slopes are from 380° to 85°, just as steep as it is 
possible for such material to lie. The original form of the 
crater, which is marked by a pit over two hundred feet deep in 
the summit of the cone, is perfectly preserved. Upon its 
barren slopes the only vegetation seen is one small bush, but 
within the crater rim hidden from general view, there are a few 
pines whose trunks are several inches in diameter. 
The lava field resembles an immense tabular stone pile cov- 
ering an area of about three square miles, and ending upon all 
sides with steep slopes like a terrace over a hundred feet in 
height. Its surface, although champaign, is extremely rough, 
