SO-CALLED PORPHYRITIC GNEISS OF NEW HAMPSAIRE 717 
(hornblende). granite in the bed of the Mad River. If this 
hypothesis be correct, the Conway granite is younger than the 
porphyritic granite, for at about 1800 feet above the river the 
porphyritic phase distinctly cuts the coarser rock. 
The Ashuelot area—The country rock about the porphyritic 
granite of the Ashuelot area is referred by the survey to three 
different formations. the Bethlehem gneiss, the schists of the 
Coés group and the Montalban group. Specific reference to this 
area was made in the second volume of the Survey Report. In 
3P, 470. 
their general correlation, the survey considered the markedly 
oval form of this and other occurrences of the porphyritic 
granite as allying it in point of age to similarly shaped masses 
in the Archzan elsewhere. Such a form has a nearer homo- 
logue to the batholites described by Emerson in western Massa- 
chusetts, and as we shall see, these similar forms have similar 
origins. That the porphyritic granite of the Ashuelot area is 
eruptive and of an intrusive nature can be amply proved. We 
shall not attempt to trace the evidence from the contact- 
phenomena, as it might be traced in a complete description of 
the whole boundary. It is of the same nature as that outlined 
for the Winnipiseogee area. With that fact in mind, we have 
considered it expedient to refer to a few only of the possible 
localities which can be readily visited for confirmation of our 
views. 
A representative contact of the porphyritic granite and 
Coés mica-schist outcrcps where the boundary line between them 
crosses the road running southwest from Ashuelot over Gun 
Mountain. Here and along the western ridge of Gun Mountain 
the typical biotite-muscovite-schist is strongly charged with 
interbedded actinolite-schist and quartzite. Several apophyses 
of the porphyritic granite cut the schist. One of them, twenty 
feet wide, cuts across the strike, extending a considerable 
distance from the contact before it disappears under the soil- 
cap ; another over two feet in width is also well exposed, but lies 
nearly in the planes of schistosity. Horses of schist are embed- 
