^Mctauwrphosis ■:cifli0!it Cmsltiiig. — Emerson. 75 
huter has been made slaty by pressure ; and it seems to be a 
result of this pressure that a considerable quantity of fine 
granular titanite has developed at the expense of the magne- 
tite. 
It is remarkable how little breaking up of the long needles 
has attended the production of the slaty cleavage in this 
Whately rock. 
II. A PORPHVRITIC MICA SCHIST WITH POSSIBLE RIPPLE MARKS. 
The block represented by figure 2 was broken from a 
large boulder in a deep valley east of the road 3 miles south- 
east of vSouth Monson. It is typical of the Brimfield schist 
of the region. It has a chocolate shade from the abundant 
biotite. It is porphyritic with many large grains of feldspar 
which simulate pebbles perfectly. Each individual is a single 
cleavage piece nearly an inch long of a limpid moonstone. 
It is the adularia which from early times has been cited from 
Brimfield. It is a microcline of exceedingly fine grain, and 
seems by quite high power to be an ideal untwinned ortho- 
clase. Each individual has a perfect egg or ellipsoidal shape 
as if it had been turned in a lathe out of a large crystal. At 
the lower right-hand corner are two such pebble-like forms 
and directly above is a still more perfect one slrowing two 
broad cleavage surfaces but so limpid that it shows dark and 
inconspicuous in the picture. The one in the lower right- 
hand corner has grown directly across the bedding and dis- 
torted it. The banding is wrapped and wrinkled around them 
and the "pebbles" are slightly drawn out in points. 
There is a delicate and thin layer of finely granulated feld- 
spar surrounding each of the "pebbles" and derived possibly 
from their incipient crushing. A half inch layer at the bottom 
of the block is seen to be of a darker color than the rest. It 
was originally more rusty and is now more biotitic. The 
upper 'surface had distinctly the undulating surface of ripple- 
marking which has been interrupted by the later growth of the 
large feldspar grain. 
Although these later felds])ars have grown in the mass and 
biotite has developed abundantly I think it probable that this 
is really a ripple-marking. 
The way these rounded crystals of microcline have grown 
in place in the sandstone as it was becoming a schist is not 
