240 The American Geologist. ^p"'- i^^^^ 
that here the schists are on the east and the slates, quartzytes 
and Hmestone on the west of the serpentine. 
The serpentine is mainly confined to low levels, and higher 
the slates and quartzytes rest directly on the mica schist and 
the contact appears to be unconformable. It seems that the 
schist series was tilted to the eastward at a considerable angle 
and the Devono-Carboniferous laid down arcoss the beveled 
edges of its strata. Similar evidence of non-conformity was 
obtained on Hay Fork mountain. If the serpentine is older 
than the schists there will not be any difficulty in demonstrat- 
ing an unconformity indicating an immense erosion of the 
schists previous to the deposition of the Devono-Carboniferous 
sediments, but if the peridotyte was intruded into schists 
and slates, the unconformity rests upon less definite evidence 
and more work will be required to establish the fact beyond the 
possibility of doubt. However, it is a fact that the typical De- 
vono-Carboniferous comes close up to the typical schists and 
they are separated by a sharp line, not the least evidence of one 
grading into the other having ever been found. 
Throughout the Devono-Carboniferous areas, narrow belts 
or so-called "dikes" of serpentine are rather common. They us- 
ually outcrop at lower levels, the schistose slates and quartzytes 
apparently curving up over them as does the Bragdon slate 
over the Clear Creek greenstone in the folds of Trinity valley. 
One such strip of serpentine forming the axis of a narrow fold 
occurs in Bridge gulch in the Hay Fork section. The typical 
schistose slate and quartzyte of the Devono-Carboniferous 
overlie it and may be traced to the ver}- contact practically 
tmchanged. In the Scott valley region south of Fort Jones in 
Siskiyon county, a sheet of serpentine appears to underlie the 
Devono-Carboniferous over at least several square miles. In 
no instance have I observed the development in these Devono- 
Carboniferous areas of a mica schist or a graphite schist or a 
hornblende schist along the contact, such as constitute the 
Abrams and Salmon formations. It would be too remarkable 
a case of selection to suppose that the peridotyte converted 
thousands of feet of strata into mica and hornblende schists in 
one area, and that in an immediately adjoining area, equally as 
large masses of peridotyte failed to develop in the same strata 
even a narrow contact zone of similar schist. The inference 
