Califoniian Metauwrphic Formations: — Hcrshey. 243 
Paleozoic era, there occurred another uplift and tilting of the 
strata. The Devono-Carboniferous formations zvere metamor- 
phosed to nearly their present degree, while in the earlier series 
which had previously been converted into schists, there ivas an 
intensifying of the metamorphism. In the Jurassic there came 
another submergence with the deposition of the Bragdon slates, 
followed by the uplift, folding, faulting and fracturing of the 
strata to which the present Klamath mountains structurally are 
due. During this orogenic disturbance, the Clear Creek green- 
stone and Bragdon slates were well lithified, partially silicified, 
and a schistose structure developed along certain limited shear 
zones ; in other words, the Jurassic series was slightly meta- 
morphosed. At the same time there -was another intensifica- 
tion of the alteration of the schists and Devono-Carboniferous 
series. This theory so well explains the facts observed in the 
mountains that it is hardly necessary to call into play possibili- 
ties w^hich are not strong probabilities. 
It is true that there are throughout the Klamath region cer- 
tain narrow zones of metamorphism due to the intrusion of 
various acidic and basic dikes, and they have produced even 
in the Jurassic slates, schists of somewhat similar mineralogical 
composition to the Klamath series, but the local character of 
the former is always manifest and there is no reason for con- 
fusion. In this paper I am considering only the alteration that 
is regional in character, affecting entire formations over many 
hundred square miles. In the case of the Klamath schists this 
was probably due to their having been deeply buried under 
other sediments and brought under the influence of the internal 
heat of the earth. The regional alteration of the Devono- 
Carboniferous and Jurassic series is mainly of a dynamical 
character. Upon this is locally superimposed the thermo-met- 
amorphism of the central zones. 
We are now ready to consider the question of the age of the 
schists. They contain no fossils and manifestly our conclusion 
must be provisional and subject to modification at any time. 
I feel safe in asserting that they are considerably older than 
the Devono-Carboniferous series. They seem to be separated 
from the latter by a non-conformity of no mean value and cer- 
tainly by a great difference in degree of metamorphism. The 
relation in point of metamorphism between the Jurassic, De- 
