Agricola, Georgius, De re metallica, 1912/1950

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              <s>
                <pb pagenum="31"/>
              are exposed before his eyes. </s>
              <s>There are just as great differences in hills as
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              there are in mountains, yet the miner does not dig except in those situated
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              in mountainous districts, and even very rarely in those. </s>
              <s>It is however very
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              little to be wondered at that the hill in the Island of Lemnos was excavated,
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              for the whole is of a reddish-yellow colour, which furnishes for the inhabit­
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              ants that valuable clay so especially beneficial to mankind
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              10
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              . </s>
              <s>In like
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              manner, other hills are excavated if chalk or other varieties of earth are
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              exposed, but these are not prospected for.</s>
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              <s>There are likewise many varieties of valleys and plains. </s>
              <s>One kind is
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              enclosed on the sides with its outlet and entrance open; another has either
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              its entrance or its outlet open and the rest of it is closed in; both of these are
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              properly called valleys. </s>
              <s>There is a third variety which is surrounded on all
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              sides by mountains, and these are called
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              convalles.
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              </s>
              <s> Some valleys again,
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              have recesses, and others have none; one is wide, another narrow; one
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              is long, another short; yet another kind is not higher than the neighbouring
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              plain, and others are lower than the surrounding flat country. </s>
              <s>But the
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              miner does not dig in those surrounded on all sides by mountains, nor in those
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              that are open, unless there be a low plain close at hand, or unless a vein
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              of metal descending from the mountains should extend into the valley.
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              </s>
              <s>Plains differ from one another, one being situated at low elevation,
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              and others higher, one being level and another with a slight incline. </s>
              <s>The
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              miner should never excavate the low-lying plain, nor one which is perfectly
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              level, unless it be in some mountain, and rarely should he mine in the other
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              kinds of plains.</s>
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              <s>With regard to the conditions of the locality the miner should
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              not contemplate mining without considering whether the place be
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              covered with trees or is bare. </s>
              <s>If it be a wooded place, he who digs there
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              has this advantage, besides others, that there will be an abundant supply of
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              wood for his underground timbering, his machinery, buildings, smelting,
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              and other necessities. </s>
              <s>If there is no forest he should not mine there unless
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              there is a river near, by which he can carry down the timber. </s>
              <s>Yet wherever
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              there is a hope that pure gold or gems may be found, the ground can
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              be turned up, even though there is no forest, because the gems need only
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              to be polished and the gold to be purified. </s>
              <s>Therefore the inhabitants of
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              hot regions obtain these substances from rough and sandy places, where
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              sometimes there are not even shrubs, much less woods.</s>
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            <p type="main">
              <s>The miner should next consider the locality, as to whether it has a
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              perpetual supply of running water, or whether it is always devoid of water
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              except when a torrent supplied by rains flows down from the summits of the
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              mountains. </s>
              <s>The place that Nature has provided with a river or stream can </s>
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          </chap>
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