162 : ERYTHEA. 
certain kinds of rock. The different stages of decomposition 
from the solid rock to well formed adobe may be seen near 
the summit of the hills, where the county road crosses them, 
to the eastward of the Institution for the blind and deaf- 
This rock has undergone many vicissitudes since its early 
day. Allied to the hornblende series, and in geological termi- 
nology called serpentine, it occurs in these hills under a 
variety of forms as modified by heat, pressure and glacial 
action. The large proportion of magnesia which it contains 
renders it of a greasy texture easily polished. Several modi- 
fications of this rock appear largely in mass along and near 
the summit of the hills. Alternating with this, to the south- 
eastward of the redwood, is a compact hard metamorphic 
blue rock containing sulphate of iron. This rock is much 
used in macadamizing streets. Immediately to the eastward of 
this, on the northern slope of the range, it is exceedingly 
compact and exhibits crystals of calcium. Then to the south- 
eastward again, about a mile beyond Mills’ College, is a large 
hill of jasper, beyond which there crops out a metamorphic 
rock, fragments of which are scattered over a large area. 
Such is a very general and imperfect account—imperfect 
because so general—of the locality on which this singular 
portion of the redwood belt has retained a foothold. Perhaps 
it would be more in consonance with its history to speak of 
it as having survived the exterminating casualties which have 
interrupted the continuity of the forest to the northward and 
southward from this point. 
One particular portion of this redwood tract under dis- 
cussion lies just below and to the westward of the highest 
point of the Oakland Hills. It occupies a small depression 
in the hill somewhat resembling a moraine, about two acres 
in extent. In this small area, on my first visit to the locality, 
which was in 1855, there were about a hundred and filty 
stumps of redwood, the great majority of which were from 
twelve to twenty feet in diameter, the trees having been cut 
from one to eight feet above the surface of the ground. One 
