15i 
MINERALOGY OF ST JOHN'S, 
either side of the imuth of the Narrows. The opposite 
sides of the Narrows rise very rapidly from the sea to a 
considerable height. The highest part of the trap-tuff 
formation is about 300 feet above the sea; its thickness 
about 500 yards. The trap-tuff passes very gradually, and 
most beautifully, into the next rock, which is amygdaloid. 
In this passage of the one rock into the other, the stratified 
structure is still retained, one stripe or narrow stratum 
being distinctly marked trap-tuff, the next amygdaloid ; 
the stripes of the former being broadest at first, gradually 
becoming narrower and less defined, till the amygdaloidal 
rock entirely prevails. 
The strata of the amygdaloid also run in the direction 
of NE. by N. and SW. by S., and dip likewise to the 
NW. at an angle of about 65°. The basis of this rock, like 
that of the trap-tuff, consists of minute grains of quartz, 
felspar, and claystone. The imbedded portions are invari- 
ably of a red, smooth, hard claystone : they seldom have 
the amygdaloidal form, but are square or rhomboidal, or 
in longish slates. The greater part of the amygdaloidal 
rock is entirely destitute of these portions, while, on the 
other hand, more than one half of some of the strata is 
composed of them. The amygdaloid is frequently distinct- 
ly stratified, each stratum being a few feet thick. 
The trap-tuff and amygdaloid are both of a reddish 
colour; the latter, however, sometimes occurs of a grey 
colour. The greatest height of the amygdaloid formation 
is 500 feet * ; its thickness is about three or four hundred 
yards, extending from the top of Signal Hill to the foot of 
the Crow's Nest 
Resting upon the amygdaloid is found the greenstone, 
* This is the height of Signal Hill, the highest part of the formation. 
