Journey through Souths North mid East Iceland. 161 
inclined to view these beds as streams of lava, formed at diffe- 
rent periods. With the exception of Malefell, and the Tinda- 
stoll, which are to be considered as the extremities of a moun- 
tain-range, and which exceed all the mountains of the range in 
height, all the other mountains appear of the same elevation, 
and have a tabular form The beds of which these hills are 
composed, are the following : — a. Calcedony-wache. b. Amyg- 
daloid. c. Amygdaloidal Porphyry, d. Trap-porphyry, e. 
Greenstone, f. Basalt, g. Stilhite-wacke. h. Amygdaloid, with 
Chabasite ; and generally we have again the same succession, be- 
ginning with calcedony-wacke On the Tindastoll, particu- 
larly on the east side, I almost fancied myself in the vicinity of 
Schemnitz in Hungary. I found here the whole formation of 
that neighbourhood. I observed very characteristic varieties of 
clay-porphyry, which often pass into hornstone-porphyry ; also 
pitch stone-porphyry, pearlstone-porphyry, and obsidian-porphy- 
ry. I was particularly struck with the rock-crystals, which we 
observed lining the cavities of the calcedony-wacke, and which, in 
hand-specimens, could not be distinguished from those found in 
the mine of St Stephan in Hungary. The base of Tindastoll, as 
well as that of the whole mountain-range on the Firth of Skaga, 
is clinkstone-porphyry, to which also the porphyries just enume- 
rated belong. All the mountain-ranges of Iceland which bound 
longitudinal valleys, are disposed conformably with the dip of 
the strata of the clinkstone-porphyry ; and I was surprised to 
find, that while the unaltered rocks extend from S.E. to N.W. 
the volcanic occupy a ridge extending across these from S.W. to 
N.E. J. I ascended the Tindastoll from its east to its west side, 
partly with the view of examining the rocks in which the obsi- 
dian, which occurs loose at its foot, is contained, and partly 
to explore the wacke, in which I expected to find the pre- 
cious opal; but the frightful and inaccessible nature of the 
* There is a view of the tabular trap-hills of the Skagafiord in the 2d volume 
of Henderson’s Journal. They very much resemble the trap hills in Sky, Mull, 
and other parts of Scotland, — Ed. 
■}" Menge names the beds from the predominating inclosed mineral : thus, in the 
calcedony-wacke, it is calcedony which is the principal included mineral. — Ed, 
X It would appear from the observations in the text, that the volcanic rocks form 
a great ridge across the Neptunian trap-rocks. — E d. 
VOL. II. NO. 5. JANUAKY 18S0. 
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