De Re Metallica Part 8

[Ill.u.s.tration 53 (Veins in mountain): A--Wide _vena profunda_.

B--Narrow _vena profunda_.]

_Venae profundae_ differ greatly one from another in width, for some of them are one fathom wide, some are two cubits, others one cubit; others again are a foot wide, and some only half a foot; all of which our miners call wide veins. Others on the contrary, are only a palm wide, others three digits, or even two; these they call narrow. But in other places where there are very wide veins, the widths of a cubit, or a foot, or half a foot, are said to be narrow; at Cremnitz, for instance, there is a certain vein which measures in one place fifteen fathoms in width, in another eighteen, and in another twenty; the truth of this statement is vouched for by the inhabitants.

[Ill.u.s.tration 54a (Veins in mountain): A--Thin _vena dilatata_.

B--Thick _vena dilatata_.]

_Venae dilatatae_, in truth, differ also in thickness, for some are one fathom thick, others two, or even more; some are a cubit thick, some a foot, some only half a foot; and all these are usually called thick veins. Some on the other hand, are but a palm thick, some three digits, some two, some one; these are called thin veins.

[Ill.u.s.tration 54b (Seams in the Rocks): A, B, C--Vein. D, E, F--Seams in the Rock (_Commissurae Saxorum_).]

_Venae profundae_ vary in direction; for some run from east to west.

[Ill.u.s.tration 55a (Seams in the Rocks): A, B, C--Vein. D, E, F--_Seams in the Rocks_.]

Others, on the other hand, run from west to east.

[Ill.u.s.tration 55b (Seams in the Rocks): A, B, C--Vein. D, E, F--_Seams in the Rocks_.]

Others run from south to north.

[Ill.u.s.tration 56 (Seams in the Rocks): A, B, C--Vein. D, E, F--_Seams in the Rocks_.]

Others, on the contrary, run from north to south.

The seams in the rocks indicate to us whether a vein runs from the east or from the west. For instance, if the rock seams incline toward the westward as they descend into the earth, the vein is said to run from east to west; if they incline toward the east, the vein is said to run from west to east; in a similar manner, we determine from the rock seams whether the veins run north or south.

[Ill.u.s.tration 57 (Compa.s.s)]

Now miners divide each quarter of the earth into six divisions; and by this method they apportion the earth into twenty-four directions, which they divide into two parts of twelve each. The instrument which indicates these directions is thus constructed. First a circle is made; then at equal intervals on one half portion of it right through to the other, twelve straight lines called by the Greeks [Greek: diametroi], and in the Latin _dimetientes_, are drawn through a central point which the Greeks call [Greek: kentron], so that the circle is thus divided into twenty-four divisions, all being of an equal size. Then, within the circle are inscribed three other circles, the outermost of which has cross-lines dividing it into twenty-four equal parts; the s.p.a.ce between it and the next circle contains two sets of twelve numbers, inscribed on the lines called "diameters"; while within the innermost circle it is hollowed out to contain a magnetic needle[3]. The needle lies directly over that one of the twelve lines called "diameters" on which the number XII is inscribed at both ends.

When the needle which is governed by the magnet points directly from the north to the south, the number XII at its tail, which is forked, signifies the north, that number XII which is at its point indicates the south. The sign VI superior indicates the east, and VI inferior the west. Further, between each two cardinal points there are always five others which are not so important. The first two of these directions are called the prior directions; the last two are called the posterior, and the fifth direction lies immediately between the former and the latter; it is halved, and one half is attributed to one cardinal point and one half to the other. For example, between the northern number XII and the eastern number VI, are points numbered I, II, III, IV, V, of which I and II are northern directions lying toward the east, IV and V are eastern directions lying toward the north, and III is a.s.signed, half to the north and half to the east.

One who wishes to know the direction of the veins underground, places over the vein the instrument just described; and the needle, as soon as it becomes quiet, will indicate the course of the vein. That is, if the vein proceeds from VI to VI, it either runs from east to west, or from west to east; but whether it be the former or the latter, is clearly shown by the seams in the rocks. If the vein proceeds along the line which is between V and VI toward the opposite direction, it runs from between the fifth and sixth divisions of east to the west, or from between the fifth and sixth divisions of west to the east; and again, whether it is the one or the other is clearly shown by the seams in the rocks. In a similar manner we determine the other directions.

[Ill.u.s.tration 59 (Compa.s.s with winds)]

Now miners reckon as many points as the sailors do in reckoning up the number of the winds. Not only is this done to-day in this country, but it was also done by the Romans who in olden times gave the winds partly Latin names and partly names borrowed from the Greeks. Any miner who pleases may therefore call the directions of the veins by the names of the winds. There are four princ.i.p.al winds, as there are four cardinal points: the _Subsola.n.u.s_, which blows from the east; and its opposite the _Favonius_, which blows from the west; the latter is called by the Greeks [Greek: Zephyros], and the former [Greek: Apeliotes]. There is the _Auster_, which blows from the south; and opposed to it is the _Septentrio_, from the north; the former the Greeks called [Greek: Notos], and the latter [Greek: Aparktias]. There are also subordinate winds, to the number of twenty, as there are directions, for between each two princ.i.p.al winds there are always five subordinate ones. Between the _Subsola.n.u.s_ (east wind) and the _Auster_ (south wind) there is the _Ornithiae_ or the Bird wind, which has the first place next to the _Subsola.n.u.s_; then comes _Caecias_; then _Eurus_, which lies in the midway of these five; next comes _Vulturnus_; and lastly, _Euronotus_, nearest the _Auster_ (south wind). The Greeks have given these names to all of these, with the exception of _Vulturnus_, but those who do not distinguish the winds in so precise a manner say this is the same as the Greeks called [Greek: Euros]. Between the _Auster_ (south wind) and the _Favonius_ (west wind) is first _Alta.n.u.s_, to the right of the _Auster_ (south wind); then _Libonotus_; then _Africus_, which is the middle one of these five; after that comes _Subvesperus_; next _Argestes_, to the left of _Favonius_ (west wind). All these, with the exception of _Libonotus_ and _Argestes_, have Latin names; but _Africus_ also is called by the Greeks [Greek: Lips]. In a similar manner, between _Favonius_ (west wind) and _Septentrio_ (north wind), first to the right of _Favonius_ (west wind), is the _Etesiae_; then _Circius_; then _Caurus_, which is in the middle of these five; then _Corus_; and lastly _Thrascias_ to the left of _Septentrio_ (north wind). To all of these, except that of _Caurus_, the Greeks gave the names, and those who do not distinguish the winds by so exact a plan, a.s.sert that the wind which the Greeks called [Greek: Koros] and the Latins _Caurus_ is one and the same. Again, between _Septentrio_ (north wind) and the _Subsola.n.u.s_ (east wind), the first to the right of _Septentrio_ (north wind) is _Gallicus_; then _Supernas_; then _Aquilo_, which is the middle one of these five; next comes _Boreas_; and lastly _Carbas_, to the left of _Subsola.n.u.s_ (east wind). Here again, those who do not consider the winds to be in so great a mult.i.tude, but say there are but twelve winds in all, or at the most fourteen, a.s.sert that the wind called by the Greeks [Greek: Boreas] and the Latins _Aquilo_ is one and the same. For our purpose it is not only useful to adopt this large number of winds, but even to double it, as the German sailors do. They always reckon that between each two there is one in the centre taken from both. By this method we also are able to signify the intermediate directions by means of the names of the winds. For instance, if a vein runs from VI east to VI west, it is said to proceed from _Subsola.n.u.s_ (east wind) to _Favonius_ (west wind); but one which proceeds from between V and VI of the east to between V and VI west is said to proceed out of the middle of _Carbas_ and _Subsola.n.u.s_ to between _Argestes_ and _Favonius_; the remaining directions, and their intermediates are similarly designated.

The miner, on account of the natural properties of a magnet, by which the needle points to the south, must fix the instrument already described so that east is to the left and west to the right.

[Ill.u.s.tration 60 (Veins in mountain): A, B--_Venae dilatatae_. C--_Seams in the Rocks_.]

In a similar way to _venae profundae_, the _venae dilatatae_ vary in their lateral directions, and we are able to understand from the seams in the rocks in which direction they extend into the ground. For if these incline toward the west in depth, the vein is said to extend from east to west; if on the contrary, they incline toward the east, the vein is said to go from west to east. In the same way, from the rock seams we can determine veins running south and north, or the reverse, and likewise to the subordinate directions and their intermediates.

[Ill.u.s.tration 61a (Veins in mountain): A--Straight _vena profunda_.

B--Curved _vena profunda_ [should be _vena dilatata_(?)].]

Further, as regards the question of direction of a _vena profunda_, one runs straight from one quarter of the earth to that quarter which is opposite, while another one runs in a curve, in which case it may happen that a vein proceeding from the east does not turn to the quarter opposite, which is the west, but twists itself and turns to the south or the north.

[Ill.u.s.tration 61b (Veins in mountain): A--Horizontal _vena dilatata_.

B--Inclined _vena dilatata_. C--Curved _vena dilatata_.]

Similarly some _venae dilatatae_ are horizontal, some are inclined, and some are curved.

[Ill.u.s.tration 62a (Veins in mountain)]

Also the veins which we call _profundae_ differ in the manner in which they descend into the depths of the earth; for some are vertical (A), some are inclined and sloping (B), others crooked (C).

[Ill.u.s.tration 62b (Veins in mountain)]

Moreover, _venae profundae_ (B) differ much among themselves regarding the kind of locality through which they pa.s.s, for some extend along the slopes of mountains or hills (A-C) and do not descend down the sides.

[Ill.u.s.tration 63a (Veins in mountain)]

Other _Venae Profundae_ (D, E, F) from the very summit of the mountain or hill descend the slope (A) to the hollow or valley (B), and they again ascend the slope or the side of the mountain or hill opposite (C).

[Ill.u.s.tration 63b (Veins in mountain)]

Other _Venae Profundae_ (C, D) descend the mountain or hill (A) and extend out into the plain (B).

[Ill.u.s.tration 64a (Veins in mountain): A--Mountainous Plain. B--_Vena profunda_.]

Some veins run straight along on the plateaux, the hills, or plains.

[Ill.u.s.tration 64b (Intersections of Veins): A--Princ.i.p.al vein.

B--Transverse vein. C--Vein cutting princ.i.p.al one obliquely.]

In the next place, _venae profundae_ differ not a little in the manner in which they intersect, since one may cross through a second transversely, or one may cross another one obliquely as if cutting it in two.

[Ill.u.s.tration 65 (Intersections of Veins): A--Princ.i.p.al vein. B--Vein which cuts A obliquely. C--Part carried away. D--That part which has been carried forward.]

If a vein which cuts through another princ.i.p.al one obliquely be the harder of the two, it penetrates right through it, just as a wedge of beech or iron can be driven through soft wood by means of a tool. If it be softer, the princ.i.p.al vein either drags the soft one with it for a distance of three feet, or perhaps one, two, three, or several fathoms, or else throws it forward along the princ.i.p.al vein; but this latter happens very rarely. But that the vein which cuts the princ.i.p.al one is the same vein on both sides, is shown by its having the same character in its footwalls and hangingwalls.

[Ill.u.s.tration 66a (Intersections of Veins): A, B--Two veins descend inclined and dip toward each other. C--Junction. Likewise two veins.

D--Indicates one descending vertically. E--Marks the other descending inclined, which dips toward D. F--Their junction.]

Sometimes _venae profundae_ join one with another, and from two or more outcropping veins[4], one is formed; or from two which do not outcrop one is made, if they are not far distant from each other, and the one dips into the other, or if each dips toward the other, and they thus join when they have descended in depth. In exactly the same way, out of three or more veins, one may be formed in depth.

[Ill.u.s.tration 66b (Intersections of Veins)]

However, such a junction of veins sometimes disunites and in this way it happens that the vein which was the right-hand vein becomes the left; and again, the one which was on the left becomes the right.

Furthermore, one vein may be split and divided into parts by some hard rock resembling a beak, or stringers in soft rock may sunder the vein and make two or more. These sometimes join together again and sometimes remain divided.

[Ill.u.s.tration 67 (Intersections of Veins): A, B--Veins dividing. C--The same joining.]

Whether a vein is separating from or uniting with another can be determined only from the seams in the rocks. For example, if a princ.i.p.al vein runs from the east to the west, the rock seams descend in depth likewise from the east toward the west, and the a.s.sociated vein which joins with the princ.i.p.al vein, whether it runs from the south or the north, has its rock seams extending in the same way as its own, and they do not conform with the seams in the rock of the princ.i.p.al vein--which remain the same after the junction--unless the a.s.sociated vein proceeds in the same direction as the princ.i.p.al vein. In that case we name the broader vein the princ.i.p.al one, and the narrower the a.s.sociated vein.

But if the princ.i.p.al vein splits, the rock seams which belong respectively to the parts, keep the same course when descending in depth as those of the princ.i.p.al vein.