354 The American Geologist. October, i»96 
feldspar, as a result of (lyiianiic action, forms '"aiij'en,'" which 
are often sheathed by mica. Quartz may also surround the 
feldspar or form wedge-shaped masses. 
A further occurrence of feldspar (orthoclase) "augen," 
mostly (Carlsbad twins, has been noted by E. Dathe* from the 
mica-gneiss of the Eulen Gebirge. 
In jSTew York state .1. F. Kemi) has observed a complete 
transition, due to crushing, from the unchanged Adirondack 
anorthosite to the gneissic form of the same rock, showing 
the abundant development of feldspar "augen,'' which are 
evidently the uncrushed i)ortions."f 
J. G. Goodchild, in his paper on "Augen Structure in Rela- 
tion to the Origin of the Eruptive Rocks and Gneiss," states 
that it results from either, 1st, the "augen" being the un- 
slieared portions, or, 2d, the "augen," consisting of crystalline 
minerals bright and unfractured, being developed subsequent 
to the shearing. A release of pressure along the shearing- 
planes in a rock which is in a state of potential fusion would 
cause fusion and give a chance for the crystals to segregate.]; 
It is evident that the present porphyritic structure of the 
Bedford rock is not the original one; and, considering care- 
fully the facts mentioned in the previous pages, there is no 
doubt of active dynamic metamorphism having been the 
cause of its alteration. 
As to the previous condition Of the rock it may have l)een 
igneous or detrital. The latter theory, however, seems to be 
precluded by the fact that none of the usual evidences found 
in metamorphic rocks, indicative of their clastic origin, are 
found in the Bedford " augen "-gneiss. Such evidences are 
the secondary enlargement of the quartz or feldspar accom- 
panied, especially in the case of the feldspar, by the presence 
of abundant inclusions; and the appearance of the water- 
worn boundar}' of the cores, unless recrystallization has been 
complete. 
The tendency to regard it as a metamorphosed igneous rock 
is therefore natural; and if this is so, it must have been 
a rock low in lime, magnesia and iron and high in alka- 
*Zeitschr. d. d. Geol. Ges., xxxv, 219. 
tLect. Notes on Rocks. S. of Mine.s Quart., xvii, 158, 1896. 
JGeol. Mag. d), i, 355, 1891. 
