'Granite and syenite' of very different respective ages; the granite is
frequently the more recent,* traversing the syenite in veins, and being, in
that case, the active upheaving agent. "Where the granite occurs in large,
insulated masses of a faintly-arched, ellipsoidal form, it is covered by a
crust of shell cleft into blocks, instances of which are met with alike in
the Hartz district, in Mysore, and in Lower Peru.
[footnote] *Bernhard Cotta, 'Geognosie', 1839, s. 273.
This surface of the granite, owing to the great expansion that accompanied
its first upheaval."*
[footnote] *Leop. von Buch, 'Ueber Granit and Gneiss', in the 'Abhandl. der
Berl. Akad.' for the year 1842, s. 60.
Both in Northern Asia,* on the charming and romantic shores of the Lake of
Kolivan, on the northwest declivity of
p. 252
the Altai Mountains, and at Las Trincheras, on the slop of the littoral
chain of Caraccas,** I have seen granite divided into ledges, owing probably
to a similar contraction, although the divisions appeared to penetrate far
into the interior.
[footnote] * In the projecting mural masses of granite of Lake Kolivan,
divided into narrow parallel beds, there are numerous crystals of feldspar
and albite, and a few of titanium (Humboldt, 'Asie Centrale', t.
Pages:
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532