TABIETIES OF BOOR. 
81 
The griinsteins of Tucutunemo, which we consider as 
constituting the same formation as the serpentine rock, 
contain veins of malachite and copper-pyrites. These same 
metalliferous combinations are found also in Franconia, in 
the griinsteins of the mountains of Steben and Lichtenberg. 
"With respect to the green slates of Malpaso, which have all 
the characters of transition-slates, they are identical with 
those which M. von Buch has so well described, near 
>Schbnau, in Silesia. They contain beds of griinstein, like 
Si 6 s |‘^ es °f the mountains of Steben just mentioned.* 
The black limestone of the Morros de San Juan is also 
a transition-limestone. It forms perhaps a subordinate 
stratum in the slates of Malpaso. This situation would be 
analogous to what is observed in several parts of Switzer- 
tv* j a 6 1 s ^ a ^ r zone > tke centre of which is the ravine of 
rieclras Azules, appears divided into two formations. On 
some points we thmk we observe one passing into the other. 
the grunsteins, which begin again to the south of these 
slates, appear to me to differ little from those found north 
ot the ravine of Piedras Azules. I did not see there any 
pyroxene ; but on the very spot I recognized a number of 
crystals m the amygdaloid, which appears so strongly linked 
to the griinstein that they alternate several times. 
The geologist may consider his task as fulfilled when he 
has traced with accuracy the positions of the diverse strata : 
and has pointed out the analogies traceable between these 
positions and what has been observed in other countries 
But how can he avoid being tempted to go back to the origin 
of so many different substances, and to inquire how far the 
dominion of fire has extended in the mountains that bound 
e great basin of the steppes ? In researches on the posi- 
tion ot rocks we have generally to complain of not sufli- 
cientiv perceiving the connection between the masses, which 
we believe to be superimposed on one another. Here the 
* On advancing into the adit for draining the Friedrich- Wilhelmstollen 
^ caused to be begun in 1794, near Steben, and which is yet 
only d40 toises long, there have successively been found, in the transition- 
sae subordinate strata of pure and porphyritic griinstein, strata, of 
Lyman stone and ampelite (alatnwchiefer), and strata of fine-grained 
e * l ^ eln : these strata characterise the transition-slates. 
T ror instance, at the Glyshorn, at the Col de Balme, &c. 
VOL. II 
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