214 The American Geologist. -^i"''- i^^i. 
imens collected from a 40-foot dike cutting the porphyritic 
granite-gneiss near Camak on the Brinklley place, yielded the 
writer the following results : 
SiOo : 68.76 
AI2O3 16.80 
FeaO.s 0.99 
CaO 2.72 
MsO 1.00 
Na20 4.82 
K2O 3.70 
Ignition 0.29 
Total 99.08 
A comparison of this analysis with analyses of the normal 
even-granular granites reveals practically no difference. The 
acidity, as will be observed, is essentially the same. 
In addition to the quartz, feldspar varieties and biotite, thin 
sections showed inclusions of apatite and zircon, and drop-like 
inclusions of quartz and feldspar grains in the larger feldspar 
individuals, along with rounded disks of micropegmatitic inter- 
growths of quartz and feldspar. [Plate XXII, figure 2.] 
Contact phenomena : In all cases where contacts of the 
granitic rocks and schists were visible, they were, in the opin- 
ion of the writer, plainly eruptive. Although many contacts 
have been examined, they are not so numerous as might be ex- 
pected, on account of the deep covering of residual decay. 
The line of contact is usually sharp and somewhat irregular in 
the localities where best exposed. No considerable contact 
metamorphism of the surrounding rocks was visible, however, 
in any exposure. Since the surrounding rocks are equally 
completely crystalline, as a result of profound metamorphism, 
any considerable alteration would hardly be expected. Many 
granite intrusions into crystalline rocks showing little or no 
contact metamorphism have been observed in dift'erent locali- 
ties by various writers. None of the commonly associated 
minerals of contact phenomena are present in the sections exam- 
ined. In some areas, garnets, and tourmaline are very com- 
mon, but their occurrence is as frequent away from the contact 
as near it, and cannot be considered a result of contact met- 
amorphic action between the rocks. In no case has any definite 
gradation from the acid rocks into the schists been observed in 
the field, but the two appear strongly differentiated. 
