Geology and Mineralogy. 153 
faulting may have commenced earlier, the greater portion of the 
displacement has taken place since the deposition of a large part 
of the auriferous gravels and the beginning of the great volcanic 
outbursts in the vicinity of Lassen’s Peak. If we may accept 
numerous small earthquake shocks as evidence, the faulting still 
continues. The distribution of the rocks of the Chico group 
indicates that the western coast of the continent at that time lay 
along the western base of the Sierra, extending around the north- 
ern end of the range in the vicinity of Lassen’s Peak and stretch- 
ing far northeasterly into Oregon. Off the coast lay a large 
island which now forms northwestern California and the adjacent 
portion of Oregon. This island extended as far southeast as the 
Pit river region where it was separated from the main land by a 
wide strait. All of the ridges developed out of the Cretacean 
island belong to the Coast range. 
The voleanic ridge of Lassen’s Peak lies between the northern 
end of the Sierra Nevada and the Coast range. The great vol- 
canic field of Oregon and Washington Territory, to which 
Lassen’s Peak and the Cascade range belong, appears in a gen- 
eral way to be outlined by the depression between the Cretacean 
island and the main land. A general account of the facts from 
which these conclusions are drawn will appear in Bulletin of the 
U.S. Geological Survey No. 33. 
2. The Taconic System.—In a paper read before the Philo- 
sophical Society of Washington, January 15th, 1887, entitled 
“Geologic Age of the Lowest Formations of Emmons’s Taconic 
System,” Mr. Cuas. D. Watcorr considered: 1st. That he had 
tound the fauna of the lowest formation of the original Taconic 
(the Granular Quartz) to belong to the Middle Cambrian or 
Georgia fauna. 2d. That the fauna of the typical ‘‘ Upper” Taconic 
rocks in Washington County, N. Y., is a part of the same fauna. 
3d. That the granular quartz and the Upper Taconic are the 
same geologic formation; the quartz rock being the shore deposit, 
and the shales, sandstones and limestones of the Upper Taconic 
being the synchronous deposit off shore, in deeper water. 4th, 
The hydromica shales beneath the limestone on the west side of 
the Taconic range are the equivalent of the Potsdam sandstone ; 
the lower part of the limestone, or, in places, the hydromica 
shales between the quartz rock and limestone representing the 
Potsdam on the east side. 5th. Professor Dana was correct in 
considering the Stockbridge and sparry limestones and the over- 
lying hydromica schists as of Lower Silurian (Ordovician) age ; 
the latter representing the Hudson River formation. 6th. Of the 
strata referred to the Taconic system in the Taconic region, the 
granular quartz and the Upper Taconic still remain in it as pre- 
Potsdam formations, and the Stockbridge and sparry limestones 
and the superior hydromica schists are referred to the Lower 
Silurian (Ordovician) system. 
Reference was made to the bearing of these generalizations on 
the use of the names Taconic and Cambrian; the former being 
