212 TRANSACTIONS OF THE [Apr. 24 
of mica and the large amount of recrystallization, is due the 
lack of foliation. That the garnet has been formed at the 
expense of biotite originally present is not improbable. 
The contact of granite with crystalline limestone has pro- 
duced some noticeable changes in the latter. Most apparent is 
a whitening of the rock, with an increase in the coarseness of 
grain, At the same time scales of graphite and mica become 
larger and more abundant, while knotty masses of silicates 
develop to a considerable extent. Microscopic examination of 
these shows the presence of biotite, muscovite, tremolite and a 
colorless pyroxene. These minerals are crowded together in 
such a way that there is no opportunity for the development of 
crystal boundaries. Similar lumps of silicates are by no means 
wanting in the limestone at a distance from the granite, but 
near the latter rock they have developed in unusual abundance. 
On the whole the contact phenomena are not very marked, and 
some of the minerals most common in granite-limestone contacts 
are absent, 
CRYSTALLINE LIMESTONE, 
The limestone is, on the whole, quite uniform in composition 
and structure, though variations from the normal type pro- 
duced by the presence of different minerals, are common. The 
normal rock is coarsely crystalline, varies from white to dark 
gray, and contains abundant mica and graphite. Weathering 
gives a darker color to the surface, while the cleavage faces be- 
come roughened by parallel ridges, due to solution along basal 
twinning planes. 
Pyroxenic phases of the limestone are quite common, The 
pyroxene is, as a rule, colorless, and has a high extinction angle. 
It seldom shows distinct crystal outline, being in irregular 
grains of small size. Tremolite is also found, occurring in a 
similar way, but seemingly Jess abundant than pyroxene. 
Probably cenetically connected with these phases of the lime- 
stone is the serpentineous variety, though the connection has 
not been absolutely proved. The serpentine forms rounded 
grains in the rock, sometimes equalling the calcite in quantity. 
Merrill * has shown for similar rocks in Warren County that 
the serpentine is derived from pyroxene. In the present in- 
stance no serpentine has been found containing a core of pyrox- 
ene; but its structure is often such as would result from its 
derivation from pyroxene, or from hornblende, and as _ these 
* Merrill, G. P. On the Ophiolite of Thurman, Warren Co., N, Y., with 
remarks on the Hozoon Canadense; Am. Jour, Sei- IIL, XXXVII, p. 189, 
