Personal Narrative Of Travels To The Equinoctial Regions Of America During The Years 1799-1804 - Volume 3 - By Alexander Von Humboldt And Aime Bonpland.
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That region presents a very remarkable
loxodromism with the strata of mica-slate, grauwacke, and the
orthoceratite limestone of the Alleghenies, and that vast extent of
country (latitude 56 to 68 degrees) lately visited by Captain
Franklin.
The direction north-east to south-west prevails in every
part of North America, as in Europe in the Fitchtelgebirge of
Franconia, in Taunus, Westerwald, and Eifel; in the Ardennes, the
Vosges, in Cotentin, in Scotland and in the Tarentaise at the
south-west extremity of the Alps. If the strata of rocks in Venezuela
do not exactly follow the direction of the nearest Cordillera, that of
the shore, the parallelism between the axis of one chain, and the
strata of the formations that compose it, are manifest in the Brazil
group.* (* The strata of the primitive and intermediary rocks of
Brazil run very regularly, like the Cordillera of Villarica (Serra do
Espinhaco) hor. 1.4 or hor. 2 of the compass of Freiberg (north 28
degrees east.))
SECTION 3.
NATURE OF THE ROCKS.
RELATIVE AGE AND SUPERPOSITION OF THE FORMATIONS.
PRIMITIVE, TRANSITION, SECONDARY, TERTIARY, AND VOLCANIC STRATA.
The preceding section has developed the geographical limits of the
formations, the extent of the direction of the zones of
gneiss-granite, mica-slate-gneiss, clay-slate, sandstone and
intermediary limestone, which come successively to light. We will now
indicate succinctly the nature and relative age of these formations.
To avoid confounding facts with geologic opinions I shall describe
these formations, without dividing them, according to the method
generally followed, into five groups - primitive, transition,
secondary, tertiary and volcanic rocks.
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