238 The American Geologist. ^p'"'*' ■'^^*^^- 
mountains l_viiig cast of the Sacramento river. As already 
intimated, the present writer does not desire to go at length 
into the structure of that territory as it has been thoroughly 
studied by Diller whose report on it is not yet issued, but cer- 
tain general facts have long been kncnvn to the geologic public 
and may be detailed as follows: A considerable area lying just 
east of the schist belt, in eastern Trinity and western Shasta 
counties, is mainly occupied by the Clear Creek volcanic series 
and the Bragdon slate series. Small isolated areas of Devon- 
ian strata appear in this territory in a way toi indicate that this 
Mesozoic series is immediately underlaid over a considerable 
extent by Devonian rocks. These Devonian rocks come out in 
force from under the Mesozoic rocks east of the Sacramento 
river. The same Devonian belt extends northward and west- 
ward to Scott valley in Siskiyou county, where it adjoins the 
schist area. 
As it will not seriously affect the argument, it is proper to 
disregard the Mesozoic rocks lying on the Devonian strata in 
eastern Trinity and w^estern Shasta counties and consider the 
schist belt as bounded, structurally on the east by a Devonian 
belt. This is followed eastward by a Carboniferous belt, then 
by Triassic strata (the Pit shales and the Hosselkus limestone), 
and these by Jurassic strata (the Bend shales and the Morrison 
sandstone), the latter carrying us quite to the easternmost 
point of the Klamath mountain system. 
The eastern limb of this geosyncline is mostly buried under 
the lavas and tufifs of the Lassen volcanic region, but at the 
northern end of the Sierra Nevada region we may have a sug- 
gestion of it in the presence, as mapped by Diller in the Lassen 
Peak Folio of the U. S. Geologic Atlas, of Silurian strata fol- 
lowed on the west by Devonian and this latter by a broad belt 
chiefly Carboniferous. Strata of Carboniferous and Jura-trias 
ages occurring in positions not conforming to the above ideal 
westward succession weaken the argument and I give it as 
little more than a suggestion. 
The structural features which have been described as char- 
acterizing the southern portion of the Klamath region are un- 
doubtedly not confined to that area. Their extension north- 
ward will be a matter of future observation. Southward these 
two geosvnclines must underlie the Cretaceous rocks of the 
