1896. | NEW YORK ACADEMY OF SCIENCES. 265 
tact products, where diorite breaks through crystalline limestone. 
Heated solutions and gases have been the immediate agents of 
mineral growth, and their action has been so concentrated that 
the minerals have, for the most part, developed in a large mass, 
instead of an extended zone. 
Similar phenomena are shown at a point a few rods south of 
the locality above described, but with some considerable varia- 
tions. The same minerals occur, with apatite and pyroxene de- 
cidedly predominant, the former species in particular appearing 
in quantity, while at the first locality it is quite inconspicuous. 
The minerals form a coating upon a nearly vertical wall thirty 
to forty feet long and about twelve feet high. This large surface 
is so completely covered with interlocking crystals of the vari- 
ous minerals that the rock composing the wall is entirely con- 
cealed from view. Apatite and pyroxene in crystals sometimes 
reaching a length of six inches are, as already stated, the conspic- 
uous species shown, feldspar, scapolite, phlogopite and titanite 
being less abundant. The rock upon which the minerals are 
supported is of a dark gray color and has the appearance of a 
oneiss or a plutonic rock. The material which has split off so 
as to expose the face with the minerals is a crystalline lime- 
stone. The structural relations of these two rocks are precisely 
the same as those shown by the diorite and limestone of the 
first locality, and there can be no doubt that they result from 
the intrusion of the gray rock into the limestone. Sections of 
the gray rock do not, as in the previous case, give positive evi- 
dence in support of this view; neither, on the other hand, do 
they offer anything against it. The rock is a granular aggre- 
gate of feldspar with bright green pyroxene, a little hornblende 
(probably secondary), some biotite and considerable titanite. 
The feldspar is, in most sections, largely twinned, but some un- 
twinned grains are always present and occasionally they become 
most abundant. Thus the rock might be classed, so far as this 
evidence goes, as a rather acid gabbro, or perhaps as a member 
of the intermediate group of monzonites. So far as structure is 
concerned, it might be either an igneous rock or one of the 
pyroxene gneisses of doubtful origin. But the field evidence is 
sufficient to establish its igneous nature, while its structure is 
closely analogous to parts of the Russell gabbro recently 
described by the writer,* and it is not improbable that further 
investigation might show the rock to be of this nature. But for . 
present purposes it is sufficient to know that it is intrusive, for 
this establishes clearly the origin of the second group of min- 
erals. It is another instance of contact action; and while the 
* Am. Jour. Sci. (4) I., p. 278. 
TRANSACTIONS N. Y. ACAD. Scr., Vol. XV., Sig. 18, Dec. 11, 1896. 
