Geoscience Reference
In-Depth Information
were originally thought to resemble rams' horns - horns which Amun
was often depicted wearing as a head-dress.
The year before his professorial appointment Bergman published
a weighty volume titled Physical Description of the Earth. This
volume was revised and expanded into two volumes published in
1773 and went into several foreign language editions. Bergman's geo-
logical opinions and observations were widely disseminated and may
even have influenced the thinking of Werner. Bergman argued that all
rocks were precipitated from water, but that this took place episod-
ically and locally. He recognised four major divisions of strata that
were arranged in distinct layers in the Earth: the Ura˚ldrige or primi-
tive rocks, by which he meant principally crystalline igneous rocks
such as granite, or metamorphic gneisses, formed the innermost layer
and were found in the cores of mountains. The Flola˚grige or bedded
rocks, which made up the second layer, comprised sandstones, coals
and limestones, which Bergmann regarded as having been formed
from suspended materials that settled out of the waters. The sedi-
ments were derived by the erosion of the rocks of the Ura
˚
ldrige. The
third layer he termed the Hopvra
˚
kta, which broadly means 'swept
together', and these were the largely unconsolidated sediments
found on the Earth's surface. The final layer, the Vulkaner, were
volcanic products produced by melting in the deep fires thought to
be found in the interior of the globe, and subsequently erupted on to
the surface where they cooled and crystallised.
Abraham Gottlob Werner, our fourth eighteenth-century defi-
ner of a stratigraphical framework, was probably the most widely
known, as we shall see later, partly because of his role in the debate
between the so-called Neptunists and the Vulcanists. Werner was
born in Wehrau on 25 September 1749 and died at the age of 67 in
Dresden on 30 June 1817.
Werner joined the staff of the Bergakademie (mining academy)
in Freiberg ten years after its establishment by the Elector of Saxony in
1765, and to his professorship of mineralogy he later added the title
of 'Councillor for Mines in Saxony'. At the Bergakademie students
