Klamath Mountains^ California. — Hcrshey. 241 
fault blocks between. The combination of all these structural 
features has given rise to such a complexity of local dips that 
anyone crossing the country on one of the stage roads is like- 
ly to arrive at almost any kind of conclusion in regard to the 
general structure of the area. 
Subsequent to the completion of the Clear Creek volcanic 
series and apparently also subsequent to the deposition of the 
Bragdon slates, much of the Klamath region was invaded by 
huge batholiths and dikes of peridotyte, since largely altered 
into serpentine. The largest area of serpentine occurring in 
the southern portion of the Klamath region occupies the ex- 
treme northeastern part of Trinity county and adjoining sec- 
tions of Siskiyou and Shasta counties. It has a length in a di- 
rection from northeast to southwest of about forty-five miles 
and a width between five and twenty miles, but within this area 
there are other intrusives. It has chiefly invaded the Devonian 
belt east of the central schist ridge, but also extends into the 
latter and forms the northwest boundary of the Mesozoic belt. 
Next there were intruded batholiths of gabbro and pyrox- 
enyte, mainly within the serpentine areas. Another change 
in the underlying magma resulted in the intrusion of 
granite batholiths. These rise in the serpentine areas and in 
the belts of schists, Paleozoic and Mesozoic slates. Their out- 
crops usually form oval or elliptical areas, square miles in ex- 
tent, several exceeding a score. 
The intrusion of such great masses of eruptive material 
into the sedimentary rocks must have had seme efifect on the 
structure of the latter, but as yet I have failed to observe any 
strong evidences of an extensive displacement of the strata. 
The granite masses appear tO' be in the form of huge colutnns, 
rising vertically through the other rocks. In only one instance, 
namely, that of Mt. Courtney at the head of the South Fork 
of the Salmon river, do the strata seem to have been distinctly 
thrust up around a granite batholith. Here the schists have 
been upturned, so that a narrow belt of Abrams mica schist 
completely surrounds the granite. In all other cases observed, 
the granite seems to have simply replaced part of the form- 
ations intruded. Of course, in the vicinity of the contact there 
Was more or less disturbance of the stratification by the in- 
truded granite, but no such disturbance of the areal geology 
