1893. ] NEW YORK ACADEMY OF SCIENCES. 209 
making an angle of 5°, with the axis of greatest elasticity in the 
quartz, 
In nearly all sections the hair-like bodies are more or less 
bent, broken and stretched apart. Sometimes it is evident that 
this results from a-crack through the quartz, but more often it 
is impossible to detect any sign of such fracture. Apparently 
the quartz has been sufficiently plastic to yield to strains which 
broke the rutile. 
Inclusions of zircon and other small crystals or fragments in 
the quartz sometimes show several short cracks radiating from 
them. A similar occurrence is also seen in the feldspar. In 
the case of cracks radiating from hornblende in a porphyritic 
rock Becker* has suggested that they might result from the 
forcible expansion of the hornblende in process of growth. But 
in the present instance it seems more probable that they result 
from the unequal resistance offered by the included mineral and 
the quartz or feldspar to the pressure to which the rocks have 
been subjected. Other effects of pressure are seen in the marked 
undulatory extinction always present, in the more or less shat- 
tering of the quartz, and in the development in it of abundant 
secondary fluid inclusions. 
There is wide variation in the character of the feldspar. In 
the normal granitite orthoclase is most abundant, in the granu- 
litic variety microcline is often conspicuous, while in the more 
basic granitite and diorite a basic plagioclase replaces the more 
acid species. 
Microperthite is common, though rather less so than in the 
gneiss. Feldspar is also sometimes intergrown with quartz, 
forming micropegmatite. As is usually the casey, this micropeg- 
matite fills small spaces between the larger rock constituents, 
and is evidently of late formation. In many instances it is 
clearly secondary, having formed in cracks made by disturbances 
subsequent to the solidification of the rock. So often is this 
true that it is highly probable that all of the micropegmatite is 
of secondary origin. Enough instances of each secondary 
formation of micropegmatite have been described} to indicate 
that it is a general, rather than exceptional, phenomenon. 
* Becker, G. F., ‘‘ Quicksilver deposits of the Pacific Slope,” p. 100. 
t Rosenbusch, Mic. Phys. Mass. Gest., p. 39- 
+ Irving, R. D., “‘The Copper Bearing Rocks of Lake Superior.’”’ Monograph 
Wee. Bac, 5 D114: 
Judd, J. W., Quart. Jour. Geol. Soc., XLV., p. 175-186. Ibid. XLITI.. p. 72. 
Romberg, J., Neues Jahrbuch, fuer Mineralogie, ete., B. B. VIII, p. 314-323; 
374-378. 
Hobbs, W. H., Bull. Geol. Soe. America, IV., p. 171. 
Transactions N. Y. Acad. Sci. Vol. XIL. July 6, 1893, 
