SO-CALLED PORPHVRITIC GNEISS OF NEW HAMPSHIRE 707 
morphic cause of crushing, as described by Howitt, Hobbs and 
other writers. 
The proportions of phenocrysts to matrix and of acid to basic 
constituents are quite constant in the porphyritic granite. The 
latter relation is that usually found in most highly acid granites. 
Now and then, a well-foliated segregational mass of biotite, 
quartz, much titanite and apatite, wrapping about phenocrystic 
cores of feldspar, may be encountered. Again, a phase of the 
rock nearly devoid of phenocrysts is not rare, although quanti- 
tatively it is insignificant as compared with the porphyritic 
phase. Both of these variations from the type will be discussed 
in what follows. 
Field relations: The Winnipiseogee area —The general dis- 
tribution of the porphyritic granite in the Winnipiseogee area is 
described at length in ‘“‘The Geology of New Hampshire.”’* 
The topography of the area is, on the whole, not of a very 
definite nature. The greater reliefs, which vary from 800 to 
1500 feet above sea level, are without distinct trends, and are 
the forms which might be expected as the result of eroding a 
massive rock of pronounced homogeneity. Upon this rolling 
ground the glacial drift has been deposited in unusual thick- 
ness, especially in the southern half of the area, where the hills 
are commonly composed of washed drift and till. Correlative 
with glacial reliefs are the glacial depressions seen in the 
numerous lakes and ponds which make such picturesque variety 
in the landscape of Carroll county. These modern deposits 
make it difficult to work out the relations of the bed-rocks. 
The variety of outcrops in many parts renders the determination 
of contact lines almost impossible, and it is largely to this cause 
that the suppositional nature of some of them is due. 
The geological relations of the Winnipiseogee area.—TVhe sur- 
vey map places the porphyritic granite of this area in contact 
with the Lake Winnipiseogee gneiss, the Montalban group of 
schists, the Rockingham mica-schist, and the vartous eruptive 
masses of Waterville. For convenience we shall briefly indicate 
Viol sip 5O2. 
