552 THE AMERICAN NATURALIST. (VOL; XXXIII. 
the change from the slate to the adinole, an actual addition of mate- 
rial from the igneous rock has taken place. 
The Granitic Rocks of the Sierra Nevadas.—Turner * describes 
the granular complex of the central and. ‘southern Sierra Nevadas 
as comprising nearly the entire range of ‘plutonic rocks. They are 
associated more or less closely with gneisses, some of which may be 
sedimentary while others are igneous. Among the rocks belonging 
in the granite family the author distinguishes seven types, a biotite 
granite, a granodiorite, a quartz monzonite, both in porphyritic and 
in non-porphyritic phases, soda-granite, aplite, potash-aplite, pegma- 
tite, and a type designated as the bridal veil granite. 
The granodiorites constitute a portion of a huge batholite, the 
parts of which have been differentiated into quartz-diorites, quartz- 
mica-diorites, quartz-hornblende-diorites, and quartz-pyroxene-dio- 
rites, gabbros, and olivine-gabbros. Typical granodiorite is an 
aggregate of plagioclase (usually andesine), quartz, orthoclase, and 
either biotite or amphibole, or both. The quartz-monzonites con- 
tain oligoclase instead of andesine. They are more acid than the 
granodiorites, as shown by the analysis below. The bridal veil gran- 
ite is a fine-grained white rock that often possesses an orbicular 
structure — the nodules consisting of a white nucleus of quartz and 
feldspar surrounded by a zone rich in biotite. 
The aplites and soda-granites are also white rocks in which albite 
is the principal feldspathic component. Quartz-diorite aplites occur 
in dykes cutting quartz-diorite. These are regarded as genetically 
connected with the more basic diorite with which they are associ- 
ated, just as the potash aplites are related to the granodiorites and 
quartz-monzonites in which these rocks occur. The feldspar of the 
quartz-diorite aplite is chiefly andesine. 
Analyses of the most important types of rocks discussed are shown 
in the following figures : 
I. 70.75 29 15.51 5 1.34 2.82 55 4.28 3.11 46 10 = 100.34 
I. 654 p 16.05 1.47 3:06 4.88 2.13 2.43 349 1.27 pores. 
III. 66.83 54 «15.24 2.73 1.66 359 163 4.463.106 = 100.82 
IV. 74.21 30 14.47 35 50 1.71 28 io  J6ł 38 o7 = 99.99 
21 17.57 2I 1.04 4.54 58 7% 4.91 55 03 = 100.09 
Ve oe 54 35 a 09 a h, 43 02 $2100.37 
I = average of three biotite-granites, II = average of five granodio- 
rites, III = quartz-monzonite, IV =soda-aplite, V = quartz-diorite 
aplite, VI = average of two potash-aplites. 
1 Journ. of Geology, vol. vii, p. 141. 
