164 The American Geologist. March, 1892" 
from sandstone or through the intermediate stage of a metamor- 
phic crystalline rock.* Contrary to the foregoing views J. 3. 
Diller speaks of the serpentines of the Coast Ranges, as altered 
peridotites.¢ That at least a part of the California serpentines. 
are altered eruptives seems also to be the opinion of H. W. 
Turner,{ W. Lingren and G. P. Merrill. 
The general similarity of the serpentines and their strati- 
graphical position lead me to believe that they are all of the same 
geological age, and, as a rule, have resulted from the decay of 
a peridotitic rock. The eruption of the peridotite and its altera- 
tion to serpentine must have taken place prior to the deposit of 
the Wallala beds, for the latter, according to Dr. Becker, contain 
serpentine boulders. 
The serpentine bodies of the Coast Range are generally more 
irregular in outline than those of the Sierras, owing to the greater 
umount of crushing which the metamorphics of the former re- 
gion have undergone, but are always sharply defined and indis-- 
tinguishable in appearance from those of the Sierras, the eruptive 
nature of which I think no one will deny. 
A slight degree of contact metamorphism is often shown. 
This is well illustrated on the road from Leesville to Bartlett's 
Springs where some pre-Cretaceous argillites have been hardened: 
and made to assume a dark metallic appearance near the contact. 
On Grindstone creek, Colusa county, the Knoxville shales have been 
metamorphosed for a distance of a hundred feet, the bedding ob- 
literated and a noticeable hardening induced. Numerous other 
instances of this were seen in Tehama and Colusa counties. In 
many cases the effect produced by the serpentine has been ob- 
literated by the movements which have taken place along the 
contact. The presence of the serpentine in dikes and irregular 
bunches in the Knoxville shales, and the inclusions of the shale 
in the former are proofs of its intrusion subsequent to the deposi- 
tion of the Knoxville beds. 
Dr. Becker bases his strongest arguments for the metamorphic 
origin of serpentine on the field relations existing about Knox- 
ville, Napa county. The locality is on the eastern edge of one 
of the greatest serpentine areas of the Coast Ranges. Along 
*Geol. of the Quicksilver Deposits, p. 121. 
*+Bull. Geol. Society of America, Vol. II, p. 207. 
Bull. Geol. Society of America, Vol. IT, p, 390. 
