95 
are united; but farther east they diverge again and for a 
hundred feet or more are separated by from one to four feet of 
compact melaphyr. Beyond that they seem to unite ; but other 
amygdaloidal bands appear below them, and toward the east 
end there are from three to five indistinct bands. These bands 
may, perhaps, be regarded as suecessive waves of lava, and 
essentially parts of one flow. At many points the amygdules 
are arranged in distinct sheets or lines parallel with the main 
bands, giving rise to а very beautiful flow-strueture, and in 
none of the Nantasket ledges is the flow-structure more per- 
fectly developed than here. Both the lines and bands dip S. 
5°—10°, the strike being N. 80° E. 
The amygdules range from pin-heads to one inch in diameter, 
and average fully one fourth inch. They are chiefly composed 
in order of importance of: (1) whitish, compact epidote (mixed 
feldspar and epidote) ; (2) quartz ; (3) feldspar, which is often 
reddish; (4) chlorite; and (5) bright green epidote. The 
compact, whitish epidote also forms many irregular veinlets, 
which conform with the flow-structure, or cut it at all angles, 
and pass insensibly into the large amygdules. In all these 
segregations, the quartz was the last mineral to be deposited. 
Quartz has not been observed in the same amygdules with 
chlorite, but feldspar, epidote, and quartz were always depos- 
ited in that order. The sequence of the minerals in the amyg- 
dules is quite varied and the following, stated in the order of 
abundance and beginning on the outside in every case, have 
been observed: (1) mixed feldspar and epidote, and quartz; 
(2) feldspar and quartz; (3) feldspar, epidote, and quartz ; 
(4) epidote and quartz; and (5) mixed epidote and feldspar, 
and chlorite. Occasionally bright red jasper occurs with the 
quartz. The amygdules were carefully examined to see if 
their elongation and orientation throw any light upon the direc- 
tion of the flow. The smaller amygdules are mainly spherical ; 
and the larger ones, although elongated, are usually very irreg- 
ular. So far ав the evidence goes, it favors the view that the 
lava eame from the east. 
