Personal Narrative Of Travels To The Equinoctial Regions Of America During The Years 1799-1804 - Volume 1 - By Alexander Von Humboldt And Aime Bonpland.
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By This Method, Hitherto Very Little Employed, On
Reducing The Heights Of The Sun To The Same Time, A Reflecting
Instrument May Be Used Like An Instrument Furnished With A Level.
I
found the latitude of the cape to be 10 degrees 36 minutes 45
seconds; I could only make
Use of the angles which gave the image
of the sun reflected on a plane glass; the horizon of the sea was
very misty, and the windings of the coast prevented me from taking
the height of the sun on that horizon.
The environs of Cabo Blanco are not uninteresting for the study of
rocks. The gneiss here passes into the state of mica-slate
(Glimmerschiefer.), and contains, along the sea-coast, layers of
schistose chlorite. (Chloritschiefer.) In this latter I found
garnets and magnetical sand. On the road to Catia we see the
chloritic schist passing into hornblende schist.
(Hornblendschiefer.) All these formations are found together in the
primitive mountains of the old world, especially in the north of
Europe. The sea at the foot of Cabo Blanco throws up on the beach
rolled fragments of a rock, which is a granular mixture of
hornblende and lamellar feldspar. It is what is rather vaguely
called PRIMITIVE GRUNSTEIN. In it we can recognize traces of quartz
and pyrites. Submarine rocks probably exist near the coast, which
furnish these very hard masses. I have compared them in my journal
to the PATERLESTEIN of Fichtelberg, in Franconia, which is also a
diabase, but so fusible, that glass buttons are made of it, which
are employed in the slave-trade on the coast of Guinea.
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