414 THE JOURNAL OF GEOLOGY. 
there are streaks of serpentine, amphibolite and quartz schists 
forming one series which is cut off by a protrusion of the large 
Merrimac granite area. The succession of the most. abundant 
of the pre-Tertiary rocks of the Sierra Nevada would then be: . 
INTERMEDIATE - Augitic porphyrites and their tuffs — effusive. 
Basic - - - -  Peridotites and Pyroxenites — intrusive. 
AcID - - - - Quartz-mica-diorites — intrusive. 
Brégger has introduced a term that promises to be of much 
use to petrographic science. He writes :* . 
For rock-types, differentiated out of a common magma, I propose the 
name ‘‘complementary rocks;’’ camptonites and bostonites are then such 
complementary rocks. 
The serpentine, a very basic rock, and the quartz-mica-diorite 
are thus perhaps later differentiations from the intermediate 
magma of the augitic porphyrite eruptions. It is obviously 
unsafe, however, to generalize on the meager data presented as 
to the age of all of the augitic tuffs, serpentines, and granites 
of the Sierra Nevada. Instead of there being one series of 
these pre-Tertiary rocks, it is much more probable that there 
are two, a Paleozoic and a Jura-Trias series, and it is far from 
improbable that the succession is more complicated than repre- 
sented here. 
Later than the quartz-mica-diorite and serpentine are the 
aplite dikes or veins and the late hornblende-porphyrite dikes, 
and these may possibly be ‘‘complementary rocks” also. Both 
are nearly of an age, but they are not found together, so far as 
the writer has observed. The dikes of hornblendic rock are 
abundant in the Spanish Peak and the Merrimac (Bidwell Bar 
sheet) and the West Point (Jackson sheet) granitic areas; and 
the aplite dikes are common in most of the granitic areas, but as 
before stated are not associated with the hornblendic dikes. 
H. W. TurRNeER. 
t Quart. Jour. Geol. Soc., Vol. L., 1894, p. 31. 
