198 TRANSACTIONS OF THE [APR. 15, 
than the orthoclase. In the groundmass it sometimes occurs in 
granular form, being then in some cases, probably in all, of sec- 
ondary origin (the rock being a consolidated ash). More gener- 
ally it is seen as little rods lying in a granular mixture of less 
well individualized feldspathic material. 
The ferromagnesian silicates are almost entirely wanting. 
This may be due in part to alteration, but they evidently were 
never in any considerable quanity. In one instance (Spec. 340 
from east. of Coldbrook Station), a quartz bearing porphyry 
with an unusual abundance of phenocrysts, biotite -has been ob- 
served, now colorless from alteration, but still retaining its 
optical characters and form. 
Magnetite and other iron ores occur commonly, mostly in 
very small grains. It is frequently titaniferous, as shown by its 
weathering to leucoxene. 
The special interest of this group of rocks lies in the charac- 
teristic structures noticeable in them. These afford conclusive 
proof that the rocks were ejected on the surface and probably 
in part under water, and that they were originally very like 
modern voleanic products—acid lavas, scoriaceous, glassy and 
brecciated towards the surface, more compact and porphyritic 
below. 
Perlitic cracks (Pl. XIII., Fig. 1) appear to be preserved in sev- 
eral specimens, but in one only were they clearly and certainly 
determined. This is part of a “felsite”’ outcrop on the Ham- 
mond River below Upham; this felsite is strongly flow-lined, 
somewhat brecciated and spherulitic in parts. The perlitic 
cracks are preserved in some brilliantly polarizing mineral 
(calcite ?), and are most easily seen with crossed nicols, though 
they are visible in ordinary light. 
In thesame flow are the best preserved examples of large spher- 
ulites that I have seen from New Brunswick (Pl. XII., Fig. 1). 
These are rather irregular in form, seldom complete, but retain 
a radial structure. They shot out from various solid bodies 
in the magma, feldspar phenocrysts, grains of magnetite, etc., 
paying no regard in their growth to the flow-lines already ex- 
isting. The rods of quartz and feldspar seem now to be broken 
down into elongated granules with straight lateral edges (Fig. A); 
but there is no evidence in the specimen that this was not the 
original structure of the spherulites. The groundmass in which 
they occur is microgranitic, and, along with the spherulites 
themselves, is filled with minute trichites, seen in Fig. A, com- 
posed of one or more curving black needles shooting out from 
a grain of magnetite. These needles are now partly broken up 
into a succession of granules, like a string of beads; in other 
