By Prof. E. REYER, PH.D., of Vienna.
The earth's crust consists in part of eruptive rocks, in part of
sedimentary rocks. Both of them have served from time immemorial for
building purposes; but at a very early period they were the only source
from which weapons and tools could be made. Subsequently metals became
known, and were employed for this purpose.
Metals are rarely met with in a pure state, but generally in
combination with oxygen or sulphur. If we examine the original material
of which the earth was composed, and which is frequently injected
through crevices in the earth's crust, and the superjacent sediment
as eruptive rock, we find it to be a mixture of different substances
of a complex nature. It contains silicon, aluminum, iron, calcium,
magnesium, potassium, and sodium. None of these are in a free state,
but are combined with oxygen. Silicon, the lighter metals, and heavy
iron do not exhibit their true metallic character, having all been
changed into stone-like compounds, "calcified by contact with vital
air," as the old chemists expressed it.
Of the heavy metals that are of such importance to civilization I
have only mentioned iron, for this alone, in its compounds, takes any
considerable part in the rock formations. Other heavy metals are met
with in smaller quantities in the rocks. They are scarcely taken into
account by geologists who consider the earth as a whole, but it is
these rare guests that are of the greatest importance to civilization.
The metals are met with as silicates in the eruptive masses; they
are also found as oxides or sulphides, scattered through different
eruptive rocks in small granules.[16] Besides these, the "ores," which
are workable metallic compounds, are here and there concentrated in
crevices or fissures, which exist in eruptive as well as in sedimentary
rocks.
_Iron_ is met with as oxide in the eruptive rocks, in fissures, and
finally in thick strata and deposits within the sediment; whole
mountains consist of iron ore.
_Tin_ occurs as oxide (tin stone), scattered through eruptive masses
rich in quartz, also in fissures.
_Copper_, combined with sulphur, is found distributed through dark
eruptive rocks, poor in silica, and also in fissures in those regions.
_Gold_ and _silver_ are mixed in smaller quantities with ores of other
metals.
All these are continually exposed to atmospheric agencies toward which
they act very differently. The oxidized ores of iron and tin do not
change their character. The sulphur compounds, at least when near
the surface, are oxidized, and hand in hand with this process goes
the partial reduction of certain metals to the metallic state. Gold
and silver, and to a less extent copper, are subject to this change;
they are unmasked and are exposed to day light, not as stones, but
as brilliant, malleable metals. Finally, the heavy ores and metallic
particles are loosened from the rocks by the destructive action of
water, floated off, elutriated, and washed. In undisturbed mountain
ranges the mineral treasures lie in masses before our eyes.
The native shining and malleable metals (gold, silver, and copper)
naturally first attracted the attention of man. They may have used the
separate nuggets for ornaments as they found them, or after hammering
them together into plates. This was surely the first step in the use of
metals. It can scarcely be supposed that this use of soft native metals
contributed much to the progress of mankind, and it is highly probable
that in those early times the noble metal had but little value. The
shining particles, as long as the natural supply lasted, seemed like
worthless tinsel. Copper, which can be made into tools and vessels,
as well as soft, poor weapons, was more highly prized. Such materials
were not, indeed, suitable and able to take the place of stone tools
and weapons; nevertheless, this working of metals served as preparation
for the more complicated work of later times. Man learned to hammer and
shape metals, and he found out that the operation was much facilitated
by heating the metal.
The discovery of iron meteorites may have had some value. In these the
smith first became acquainted with the properties of a hard metal. But
I would not attach too much importance to this. The art of working
metals is not the possession of a people that have a few meteoric
knives. In my opinion the metallurgical preparation of the hard metals
from their ores is alone decisive on this point.
The volks' sagas frequently mention some god or hero, who discovered
and taught metallurgy, yet there is scarcely any doubt that the "god,"
in most cases, was human ingenuity led by chance.
We have already seen that only certain metals are found native, while
the hard metals under normal conditions remain in the form of oxide or
mineral. They have a strong affinity for the oxygen of the air, and
can only be separated and converted into metals by powerful chemical
agents. There is _one_ substance which has a still more powerful
attraction for oxygen than those metals. This is ignited carbon, which,
in its fight with the metallic oxides, robs them of their oxygen.
Carbon has been separated from the carbonic acid of the air by the
life-giving force of the sun, and vegetable life dependent upon it. But
the isolated element waits impatiently for the impulse that will enable
it to unite with the vital air under flame and heat. Men that know how
to utilize this process of nature possess the means of resurrecting
those metallic treasures which, without its powerful assistance, would
remain forever hidden from their eyes. But accident, as we have said,
pointed out the way.
In numerous places visited by primeval man, as hunter and fisherman,
and afterward as nomad, conflagrations broke out. Not unfrequently
whole forests were burned, either intentionally or not. It could not
be otherwise than that the earth's surface would get red hot in such
places, and if a strong wind favored it, this would suffice to open
these treasures. The glowing charcoal would rob the ores of their
oxygen and leave the pure metal as melted drops or cakes.[17] Copper,
tin, and iron ores could have been reduced in this way; mankind not
only knew the result but also the method of reducing metals.
This process took place not once merely, but thousands of times in
various parts of the earth, and thus, in my opinion, metallurgy may
have become known to different races of people and at different times.
A simple trench in the ground, in which a heap of glowing coals and
some pieces of ore could be subjected to a strong draught of air,
suffices, under favorable circumstances, for the preparation of the
metal; the oldest metallurgists had scarcely any more complete means at
hand for their work.
In such primitive furnaces the well known and soft metals would
naturally be worked first, and afterward copper, tin, and iron would be
obtained from their ores. A variety of substances that occur together
in nature would be smelted together in mixtures, and different metals
would naturally be mixed and a great variety of products obtained.