238 MINERALOGY AND LITHOLOGY. 
In New Hampshire, the larger part of the rocks called clay slates are 
on the boundary between clay slate and argillitic mica schist, for the 
crystalline ingredients are quite abundant. They possess in a slight 
degree a micaceous lustre, and in them a variety of minerals are devel- 
oped. For example: the clay slate from Hanover is all filled with 
minute crystals of staurolite and garnet, and such rocks are very com- 
mon in the valley region. These minerals seem to have the capacity of 
developing under influences that are insufficient to crystallize the other 
ingredients, but when cut, their sections show them to be extremely 
impure. The staurolites, under these circumstances, have not assumed 
their usual twinned forms, but are simple crystals. Some of them are 
represented in Fig. 4 on Pl. 8. 
A clay slate from Pittsburg is all covered with round spots suggestive 
of garnet. When a section of this slate is examined, these spots are seen 
to be caused by a deposit of hydrous iron oxide, which probably has re- 
sulted from the decomposition of minute grains of iron pyrites, which is 
not uncommon in these rocks. 
The Dixville notch is a good place to note the character of the scenery 
among slaty rocks, as compared with that of granitic regions. Although 
there may be exceptions enough, the granitic hills are rounded. In the 
White Mountain notch, the view, though grand in its immensity, is made 
by gently curving lines of beauty. The Dixville notch, on the other 
hand, is rude, jagged, picturesque ; for while granite wears with difficulty 
and loses its corners first, the slaty rocks, when on edge as in the Dix- 
ville notch, cleave and break down, leaving sharp points and jutting 
edges. The difference in the character of White Mountain and Alpine 
scenery is here illustrated. 
QUARTZ SCHIST. 
Quartz schist has already been referred to in the descriptions of the 
crystalline schists; but some of these rocks bear a resemblance to sand- 
stones or conglomerates, and though in part composed of crystalline 
materials, they are also in part composed of angular grains or fragments, 
and thus they form another connecting link between fragmental and 
crystalline rocks. The half fragmental character, though often visible in 
the mass, is much more satisfactorily seen in thin sections; and in Fig. 
