Califoniian Mctauiorphic Formations. — Hcrshey. 229 
fine specimens of crystalline aggregates of actinolite. The 
graphite and actinolite schists combined usually have a thick- 
ness of no more than five to fifteen feet and in the presence of 
the broader belts of other schists on either side may escape de- 
tection in many sections unless especially searched for. 
The hornblende schist is remarkable for its uniformity 
throughout a thickness of probably not less than 2,500 feet. It 
consists of elongated or blade-shaped crystals of dark green 
and black hornblende, separated by irregular thin layers of 
white quartz, with feldspar locally developed. It is moderately 
fine-grained and its general color is a dark green ; it outcrops in 
rugged peaks of black rocks. Certain layers are highly calcar- 
eous, abounding in curiously contorted folia of crystalline lime- 
stone, even increasing to one- and two-foot layers of impure 
marble. Much of the formation has a schistosity developed by 
shearing, but in places the original lamination can be distinctly 
discerned and it is often highly contorted. There are other 
portions in which quartz is nearly absent and the rock consists 
of massive aggregates of comparatively coarse hornblende crys- 
tals, producing a type resembling a truly igneous hornblendyte. 
Indeed, hand specimens of this formation have frequently been 
identified as dioryte and even some" who correctly discriminate 
it as hornblende schist consider it an altered igneous rock. I 
propose to show that it is a highly metamorphosed sedimentary. 
The largest area of hornblende schist is traversed by the 
south fork of Salmon river between its head and the vicinity 
of the village of Cecilville. It constitutes a broad, shallow, 
synclinal trough, trending north to south and probably ten 
miles in width. On each side the strata are upturned to the ex- 
tent of allowing the mica schist to come to the surface from un- 
der them. Both north and south from the river the synclinal 
is further disturbed by the upthrust of the hornblende schist 
against huge batholiths of granite and quartz-mica-dior\'te 
At the center of the structural basin thus formed, the forma- 
tion has been less modified by metamorphic action than usually. 
The strata are but little tilted and the original bedding planes 
are quite distinct. Before its conversion into hornblende 
schist it passed through a stage of thin-bedded slate, the 
structure lines of which yet remain, Interbedded with the 
schists there is a two to four-foot layer of dark gray, fine- 
