The " A i((/eir' -Gneiss Area. — Lmjuer and Iitcs. 251 
Zircon of tlie usual tyi)e is found iu very subordinate 
amounts. 
Qiiarfz is notieeal)ly absent, only appearing in small grains 
in section 27e. 
J^Kfi/e is practicably absent from this dike, the titanit'erous 
mineral being titanite, which is in marked contrast to the 
dike at 14 in which rutile is so abundant. 
The iron ores, magnetite and titaniferous magnetite, are 
found in small grains in varying amounts. At times the mag- 
netite is plentifully developed in the hornblende and iMotite. 
Pyrite is also found. 
Some of the sections of dike 27 bear a resemblance to the 
(/rugers diorite, in which, however, the plagioclase is better 
developed and the hornblende more pleochroic, containing also 
more magnetite inclusions. 
A section of the gneiss (27) near this dike, showed abun- 
dant development of garnet as the result of contact metamor- 
phism ; and a few rather short rutile needles were noticed in 
quartz grains in this section. 
Origin of the " Auoen ''-Gneiss. 
A discussion of the probable origin of the " augen "'-gneiss, 
and the metamorphism to which it has been^subjected, would 
hardly be complete without reference to the investigations 
and conclusions of other writers, dealing with rocks of simi- 
lar appearance. 
The question of the origin of thegneissic rocks is in general 
more or less obscure. The Fordham gneiss is at present being 
studied by F. J. H. Merrill. The gneisses f)f the eastern 
Adirondack region give little decisive evidence of their origin, 
while those in the townshi]) of Gouverneur on the west side, 
investigated by C. H. Smyth. Jr., appear to be derived from 
granitic rocks ; a fact which, as suggested by J. F. Kemp, lends 
support to the theory of the granitic origin of gneisses in 
other regions. The Gouverneur gneiss differs from both the 
Fordham and "augend-gneiss on account of the microi)er- 
thitecontained in it. The rock however resembles the " augend- 
gneiss slightly in that it sometimes assumes a i)orphyritic 
phase.* 
The so-calleil '-augen" structure in i-ocks has been noted 
from a number of localities, but in most cases, especially in 
*C. H. Smith, Jr., Trans. N. V. Acad. Sci., xii, June, 189.3. 
