176 BULLETIN OF THE 
in Figure 8 with black inclusions of magnetite and clear ones of quartz 
and muscovite, and having the typical irregular flattened shape. The 
feldspars of this type have a low even polarization tint, yellow of the 
lower order even in thicker slides, where other feldspars show red and 
blue. Often without twinning, or else twinned in single halves, less fre- 
quently multiple twinned with few lamellz, they have the characters 
of the albite of the schists. Some of these areas of glassy feldspar with 
the same general characters show the double twinning of microcline. 
A variety of these feldspars is seen in Figure 7, which, having the 
same flattened irregular shape, with inclusions of muscovite, quartz, ete., 
in parallel arrangement, the same even low polarization and fresh glassy 
look, are clouded in the centre by an aggregate of dots which form a 
central area with vague boundary, but having the same polarization 
color as the outer area. With the high power these are seen to be fluid 
inclusions with moving bubble, little flakes of colorless mica or kaolin, and 
black opascite masses. 
We now come to the clastic feldspars, which are generally larger than 
those just described. Figures 1 and 2 represent typical cases. 
In Figure 1 the enlargement is fifty diameters. The feldspar polar- 
izes in one low color and has a homogeneous extinction. One cleavage 
is well developed in the slide parallel to the short edge ; the other, indis- 
tinctly parallel to the right hand edge. From the obtuse angle made 
by the two cleavages, it is evident that the section is oblique to the zone 
of either cleavage. The outer shape of the grain, as well as that of the 
inner cloudy portion, is evidently determined by the two cleavage lines, 
which is some evidence of clastic character when compared with the irreg- 
ular shape of the albitic feldspars. The cloudy look of the central por- 
tion is owing to streaks of opaque kaolinized (?) feldspar containing fluid 
cavities, specks of black opascite, and stained by yellow limonitic pro- 
ducts, which lie in the clear feldspar arranged parallel to the second 
cleavage. These are evidently areas of decomposition. As seen in the 
figure, these bands die out in the clear feldspar rim. The whole feld- 
spar shows in polarized light indistinct multiple twinning parallel to the 
second cleavage, which runs almost to the outer boundary of the clear 
rim. There occur also, scattered through the central core, little bril- 
liantly polarizing flakes of muscovite, in part arranged parallel to the 
first cleavage. These become less abundant, but of larger size, in the 
clear rim, where they are apt to arrange themselves parallel to the outer 
boundary ; near the boundary they become still larger, and sometimes 
connect with the mica outside. The outside boundary of the whole feld- 
