814 The American Naturalist. [September, 
ues to find vent, and furnishes heat for the unlucky explorer who is 
compelled to spend a night at that lofty elevation. 
“The most definite account of what may be called an historically 
recent volcanic eruption of any considerable extent in the region 
referred to at the outset has just been published in a Bulletin of the 
United States Geological Survey, by Mr. J. S. Diller. The area 
described is in northern California, in the vicinity of Lassen Peak, 
about one hundred miles southeast of Mount Shasta. Lassen Peak is 
itself a vast volcanic cone, and the center of numerous others smaller 
in size and later in origin, but all of recent geological age. The Cin- 
der Cone, which was the special subject of Mr. Diller’s researches, is 
ten miles northeast of Lassen Peak, in the vicinity of Snag Lake. 
The general elevation is here a little over 6,000 feet above the sea, and 
his cone rises 640 feet above the lowest point of its base, having a 
diameter of 2,000 feet at the bottom, and 750 feet at the top, and is 
composed of cinders which readily yield and slide down under one’s 
weight as he walks over them. 
“This Cinder Cone belongs to the earliest part of the eruption, and, 
in Mr. Diller’s opinion, cannot be much more than two hundred years 
old. At the same time with the explosive eruption that produced the 
Cinder Cone, an immense amount of volcanic sand was ejected and 
scattered about the base for a distance of eight miles in every direc- 
tion. Near the base this is between six and seven feet in depth, and 
thins out gradually toward the margin. Some time subsequent to this 
explosive outburst there took place a quiet flow of basalt, which 
poured from the southeast side of the cone, and spread itself over the 
sand, covering an area about three miles long by a little over a mile 
in width. The edge of this flow everywhere presents a precipitous 
front about one hundred feet in height, and Snag Lake is formed by 
the dam which this basalt stream has extended across the valley into 
which it flowed. 
“The data for determining the age of this eruption seem to be as 
conclusive as could be desired. Dead pine trees, with their roots in 
the original soil, can still be seen projecting above the volcanic sand of 
the first eruption, and in some instances they have been partially over- 
whelmed by the later eruption of basalt, and their decaying tops pro- 
ject from under it. But the living trees all grow upon the surface of 
voleanic sand, and near the base of the cone their roots are not long 
enough to reach the original soil. The age of the oldest of the trees 
found living does not exceed two hundred years, and that, doubtless, as 
Mr. Diller supposes, very closely marks the date of the earlier erup- 
