274 Messrs. Jackson and Alger on the 
The last of the minerals which we shall mention as occurring 
at this locality is siliceous sinter. This mineral is usually embra- 
ced in the amygdaloid, forming, in its spheroidal cavities, a flaky 
or lamellar crust, which, enveloping their entire inner surfaces, 
sometimes depends in stalactitic projections, on which may be 
observed small crystals of common limpid quartz. Its color, 
which is usually snowy-white, or greyish-white, is in a few instan- 
ces of a beautiful amethystine tint. One or two geodes of this 
substance found in the breccia, on being broken, presented 
internally a bright coating of amethystine sinter with nume- 
rous crystals of wine-yellow chabasie implanted in and beau- 
tifully contrasted with it. Many of the specimens of this sinter 
resemble those of volcanic origin, brought to this country from 
the Azores by Dr. Webster. 
The next place to be noticed along the northern shore of the 
Basin of Mines, is the Five Islands, and an eminence known as 
Tower Hill. Our description of these places will include all that 
remains to be said relative to the trap rocks, of Nova Scotia. 
These islands, grouped together in a narrow compass, are about 
ten miles from the locality last described ; they rise very abrupt- 
ly from the sea, and present, for the most part, lofty fronts of a 
picturesque character. Three of them consist almost entirely of 
trap and cannot well be examined except at low water. The 
other two are composed of red sandstone, with red and black 
shale, exhibiting the passage of these rocks into a vesicular and 
zeolitic amygdaloid, the color of which depends on the propor- 
tions in which the ingredients form a part of it; it is sometimes 
made quite black by the shale. The breccia, or trap-tuff, which 
is a constant attendant of this amygdaloid, and which seems as an 
intermediate form necessary to the constitution of the latter, is 
