I Did Not See There Any Pyroxene; But On The Very Spot I Recognized A Number Of Crystals In The Amygdaloid, Which Appears So Strongly Linked To The Grunstein 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 the great basin of the steppes? In researches on the position of rocks we have generally to complain of not sufficiently perceiving the connection between the masses, which we believe to be superimposed on one another. Here the difficulty seems to arise from the too intimate and too numerous relations observed in rocks that are thought not to belong to the same family.

The phonolite (or leucostine compacte of Cordier) is pretty generally regarded by all who have at once examined burning and extinguished volcanoes, as a flow of lithoid lava. I found no real basalt or dolerite; but the presence of pyroxene in the amygdaloid of Parapara leaves little doubt of the igneous origin of those spheroidal masses, fissured, and full of cavities. Balls of this amygdaloid are enclosed in the grunstein; and this grunstein alternates on one side with a green slate, on the other with the serpentine of Tucutunemo.

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