Mineralogy and Geology of Nova Scotia. 275 
here observed, as in other places of similar character, superin- 
cumbent on the amygdaloid. To plate IV. the reader is referred’ 
for a view of a part of these Islands taken at some distance; of 
which two are shown to consist of columnar trap, besides the 
steep sugar-loaf masses, provincially termed the “Pinnacles,” 
that rise up in the rear, the highest of which is about one hun- 
dred feet, and is wholly inaccessible. The third, formed in part 
of sandstone (colored red on the plate), has been worn away on 
its west side, so as to exhibit a very fair sectional view of the 
junction of this rock with the trap ; the two, at the very point of 
contact, becoming blended as usual into trap-tuff and amygdaloid. 
The trap is not strictly recumbent on the sandstone, at this place, 
but more properly rests inclined against it. The island most 
noticed of the five, is that which stands out considerably in ad- 
vance of the others, and of which a few words only will convey 
as accurate an idea asa full drawn picture. It is composed of 
amorphous or indistinctly columnar trap, resting on a softer basis 
of amygdaloid, which has been so undermined as to leave the co- 
lumnar rock hanging over from above, like a vast leaning tower, 
and seeming at every moment as if ready to fall into the sea. 
These islands, with the exception of Tower Hill, of which 
the trap forms the summit only, are the last places along the 
shore of the Basin of Mines, at which this rock is known to occur. 
Still farther east, the sandstone, interstratified with the shale, pre- 
vails to the exclusion of every other rock. They may be regarded 
therefore, as the most distant outskirts of the trap formation 
of Nova Scotia, which, stretching east and west to the distance 
of not less than one hundred and thirty miles, forms, as a deposit 
of trap-rock, one of the most extensive and fruitful fields for mine- 
ralogical and geological research that the known world presents. 
