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BOOK V.

I have spoken of shafts, tunnels, and drifts. I will now speak of theindications given by the canales, by the materials which are dug out, and bythe rocks. These indications, as also many others which I will explain, areto a great extent identical in venae dilatatae and venae cumulatae with venaefrofundae.

When a stringer junctions with a main vein and causes a swelling, ashaft should be sunk at the junction. But when we find the stringer inter-secting the main vein crosswise or obliquely, if it descends vertically downto the depths of the earth, a second shaft should be sunk to the point wherethe stringer cuts the main vein ; but if the stringer cuts it obliquely theshaft should be two or three fathoms back, in order that the junction maybe pierced lower down. At such junctions lies the best hope of finding theore for the sake of which we explore the ground, and if ore has already beenfound, it is usually found in much greater abundance at that spot. Again,if several stringers descend into the earth, the miner, in order to piercethrough the point of contact, should sink the shaft in the midst of thesestringers, or else calculate on the most prominent one.

Since an inclined vein often lies near a vertical vein, it is advisableto sink a shaft at the spot where a stringer or cross-vein cuts them both ;or where a vena dilatata or a stringer dilatata passes through, for mineralsare usually found there. In the same way we have a good prospect of findingmetal at the point where an inclined vein joins a vertical one ; this is whyminers cross-cut the hangingwall or footwall of a main vein, and in theseopenings seek for a vein which may junction with the principal vein a fewfathoms below. Nay, further, these same miners, if no stringer or cross-vein intersects the main vein so that they can follow it in their workings,even cross-cut through the solid rock of the hangingwall or footwall. Thesecross-cuts are likewise called “ upv^rm,” whether the beginning of theopening which has to be undertaken is made from a tunnel or from a drift.Miners have some hope when only a cross vein cuts a main vein. Further,if a vein which cuts the main vein obliquely does not appear anywherebeyond it, it is advisable to dig into that side of the main vein toward whichthe oblique vein inclines, whether the right or left side, that we may ascer-tain if the main vein has absorbed it; if after cross-cutting six fathoms itis not found, it is advisable to dig on the other side of the main vein, thatwe may know for certain whether it has carried it forward. The ownersof a main vein can often dig no less profitably on that side where the veinwhich cuts the main vein again appears, than where it first cuts it; theowners of the intersecting vein, when that is found again, recover their title,which had in a measure been lost.

The common miners look favourably upon the stringers which comefrom the north and join the main vein ; on the other hand, they lookunfavourably upon those which come from the south, and say that these domuch harm to the main vein, while the former improve it. But I thinkthat miners should not neglect either of them : as I showed in Book III,experience does not confirm those who hold this opinion about veins, so now