LR. D. Irving—Hornblende of the Northwestern States. 27 
Art. IV.—On the Paramorphic Origin of the Hornblende of the 
Crystalline Rocks of the Northwestern States; by R. D. Irvine. 
among the three general classes of (1) crystalline schists, (2) 
granites and syenites, and (3) greenstones—the last term being 
used to cover all the basic massive rocks. 
and true mica-schists (biotite-schists) also occur. 
During the last three years I have examined a large number 
coln and western Marathon counties, augite-gneisses and augite- 
Schists are prominent rocks. Even in the miea-gneisses, when- 
ever hornblende appears as an accessory, augite is met with 
also.| The hornblende of all these schists is the more common 
* Geology of Wisconsin, iv, p. 617. : 
x Crystalline Rocks of the Wisconsin Valley,” by R. D. Irving and C. R. 
nhise. ogy in, i 27-704. 
Geology of Wisconsin, iii, pp. 92-99. 
Geology of Wisconsin, iv, pp. 692-696, 702-707. 
Geology of Wisconsin, iv, pp. 628, 631-635, 640-642. 
