[5 
ECONOMIC GEOLOGY 
rising through the crust-like sap in a tree. Lasius, in 1787, 
explained the ore solution as widely diffused ascending water 
(Fig. 7) which dissolved scattered grains of metals in the rocks 
through which it passed. Henkel (1679-1744), ** the Father 
of Mineral Chemistry,” recognized the evidence for the for- 
mation of lodes by replacement; but in accordance with 
the terminology of his time called it transmutation. Werner, 
the founder of the modern Freiberg school, in 1791 repudiated 
all theories based on transmutation, insisting that intrans- 
mutability is “ the fundamental pillar of chemistry; ” he 
claimed, like the lateral secretionists, that as lodes become 
poorer and thinner below, they must be filled from above or 
from the sides. These early students of ore deposits recog- 
nized facts which have only been duly appreciated within 
recent years, and their view of the ascensionist origin is 
now established for most lodes, though the ores of iron and 
manganese are mainly due to water that is percolating 
downward. 
STRUCTURE oF THE EARTH ; Its BARYSPHERE—The metals 
in the ores were originally scattered through the primary 
material of the earth. The largest part of the earth is the 
barysphere, a shell more than 3000 miles thick, and composed 
mainly of iron alloyed with nickel! The core of the earth, 
the centrosphere, about 1600 miles in diameter, is fluid as 
it does not transmit waves of distortion due to earthquakes. 
The rocky crust, the lithosphere, for which the phenomena 
of earthquakes and radioactivity suggest a thickness of about 
40 miles, may be regarded as a slag due to the lighter materials 
having floated upwards, while the heavier constituents sank 
and formed the barysphere. The weight of the earth shows 
that the bulk is metallic, and its constituents, in order of 
abundance, are probably—iron, oxygen, silicon, magnesium, 
aickel, calcium, and aluminium. 
The lithosphere was formed primarily of igneous minerals, 
which solidified from a molten state. They gave off during 
their consolidation water and gases which form the two 
outer layers of the earth, the hydrosphere or the surface 
waters, and the atmosphere. The action of water and ajr 
and sudden changes of temperature break the surface of the 
lithosphere into fragments which are deposited as beds of 
! For fuller information, cf, Tyrrell, Principles of Petrology, PP. 4-7-