Mineralogy and Geology of a part of Nova Scotia. 143 
or less proportion, as an essential ingredient of the. rock. 
The lt or trap tuff, which is a constant sites of 
the amen produced by the union of the sandstone, 
&c. which seems as-an intermediate form necessary to 
‘the ational of the latter, is here observed, as in all oth- 
er A args of similar character, superincumbent on the amyg- 
"The Island most noted among these is that, which standing 
in advance of the others, is a conspicuous object to meet the 
eye of the mariner, in his progress up the Basin. It is com- 
of amorphous or indistinctly columnar trap, which see 
ing on a Softer basis of amygdaloid, presents, from the un- 
dermining action of the surges, the curious phenomena of 
a leaning tower, and, casting a. dark, broad shade beneath 
it, seems as if ready to tumble into the sea from the over- 
hanging weight of its summit. 
On the southern front of Tower Hill is a preeipice of 
this spaces sad discover a single crys wal belonging co that fam 
ily of m ; 
y This is tl is ihe last place on the shore of iiss Baas at peas 
trap rocks are known to occur. Still farther east, si ean 
space, a field alike e nsive for tee and co 
senaaaoh: and Fapician with numerous objects of natural _his- 
a finished our account of the trap rocks forming the 
North Mountains and their outskirts, which comprise a com- 
plete Seep ene of that formation, with the more important 
and curious mineral productions which they include, and hav- 
ing suggested, aoe ‘appears to us the most obvious theory of 
their origin, which, derived from remarkable peculiarities 
of color, structure, and other appearances of contiguous 
