SO-CALLED PORPHYRITIC GNEISS OF NEW HAMPSHIRE 783 
The reader will remember how often this principle was illus- 
trated in our detailed account of contact-phenomena. It 
undoubtedly explained the greater perfection of the foliation in 
the long and narrow Winnipiseogee area than that in the 
broadly eliptical Ashuelot area or Main area. At the Benning- 
ton reservoir in the large size of the feldspar phenocrysts and 
their definite orientation with respect to the adjacent contact 
we have a good example of what characterizes the endomorphic 
zone of the Main area throughout the eastern contact as 
mapped. Within the zone the structure is much less determi- 
nate. Again, on Sandwich Mountain the porphyritic granite in 
and about the ‘‘permeation-area’”’ described above, is largely 
granitic with the exception of those parts which display the 
fluxional habit about the horses. We are not without sugges- 
tion that the sudden changes of dip and strike within the cores 
of the igneous masses are largely the result of convection act- 
ing with massive pressure in the still viscid rock-body. Two 
miles from Weirs, on the highway to Meredith village, several 
outcrops appear in a clear field some three hundred yards to the 
right of the road. At one of these, a well-marked anticlinal 
arrangement can be observed in typical porphyritic granite. 
This structure is not part of a general system of parallel folds, 
nor of folds with any recognizable relation to the behavior of 
solid rock acted upon by lateral force. It is rather to be cor- 
related with the irregular flow-structure assumed in the internal 
parts of many rhyolites; the well-known “ felsites”” of eastern 
Massachusetts furnish a good example." 
3. An analogous appearance will tend to characterize the 
margins between the intrusive rock and any foreign bodies which 
Sequence ; Q.J. Geol. Soc., 1894, p. 249. On page 265 the author says of the folia- 
tion in these Alpine gneisses that it is “‘ a contact-fluxion, and has no connection with 
the dynamo-metamorphism of the district. Thismarginal orientation also occurs on a 
microscopic scale. Mr. C. L. Whittle has described good examples in the contacts 
of the Connecticut Triassic lavas. 
BONNEY, T. G., Some Notes on Gneiss; Geol. Mag., 1894, p. 118. 
” 
Cf. MEHNER, “ Fluctuationstructur” described in certain of “die schiefrigen 
Porphyren” of Westphaiia ; Tsch. Mitth., 1877, p. 177. 
