The Slate , 
203 
dote have been secondarily developed. Some of the larger 
grains of feldspar and quartz lie with their longest diameters 
parallel to the schistosity which is sometimes feebly developed 
in these rocks. Infrequently fragments of hornblende and biotite 
occur; magnetite is an ingredient especially within the flakes of 
hornblende. Chlorite and epidote replace the hornblende, fol¬ 
lowing the lines of cleavage and finally by their development 
separating the original crystal into a number of separate frag¬ 
ments, all however perfectly oriented. Secondary muscovite is 
also an important constituent of the rock. At the immediate 
contact with the granite*, the slate has been metamorphosed to 
some degree by heat, this is indicated by the baking of the slate 
and also by the presence of small bodies or aggregations which 
resemble the knoten in the knotenschiefer of Rosenbusch. 
These bodies occurring only in the neighborhood of the granite 
are regarded as true contact phenomena. The knoten in the 
slate are aggregations of quartz, muscovite, magnetite, graph¬ 
ite, chlorite and sometimes tourmaline with rather less mica 
than the average of the rock, and thus polarizing lower. They 
are small and usually irregular accumulations of the pigments 
of the slate into more or less definite masses. In some cases 
the knoten are of sufficient size to be recognized by the unaided 
eye. There is a difference in the definiteness and regularity of 
occurrence of these bodies. The most perfect and well defined 
knoten occur in the fragments of slate which are included within 
the granite or else at the very contact. In these localities the 
coloring matter is massed together into oval knoten, with 
clearly defined limits, there is no gradual shading off into the 
mass of the rock, but the demarcation is distinct and sharp, 
outside of the knoten there is comparatively little pigment, it 
is largely gathered into the knoten. A few feet from the con¬ 
tact, the knoten are more irregular, the pigment is not accumu¬ 
lated into definite masses, but is scattered irregularly through 
the rock, though at intervals it is massed into irregular bodies 
which lack, however, the definite boundaries of the knoten at the 
contact. There is a gradual thinning out of accumulation into 
the body of the rock, it is impossible to say where the knoten 
end and the ordinary rock structure begins, as there is no sharp 
