BOOK III.	73
	But to return to veins. A great number of miners consider8 that the best veins in depth are those which run from the VI or VII direction of the east to the VI or VII direction of the west, through a mountain slope which inclines to the north ; and whose hangingwalls are in the south, and whose footwalls are in the north, and which have their heads rising to the north, as explained before, always like the footwall, and finally, whose rock seams turn their heads to the east. And the veins which are the next 8The following from Chapter iv of the Nützlich Bergbüchlin (see Appendix Β) may indicate the source of the theory which Agricola here discards :—" As to those veins which " are most profitable to work, it must be remarked that the most suitable location for the vein " is on the slope of the mountain facing south, so its strike is from vii or vi east to vi or " vii west. According to the above-mentioned directions, the outcrop of the whole vein " should face north, its gesteins ausgang toward the east, its hangingwall toward the south, " and its footwall toward the north, for in such mountains and veins the influence of the " planets is conveniently received to prepare the matter out of which the silver is to be made " or formed. . . . The other strikes of veins from between east and south to the region " between west and north are esteemed more or less valuable, according to whether they are " nearer or further away from the above-mentioned strikes, but with the same hanging" wall, footwall, and outcrops. But the veins having their strike from north to south, " their hangingwall toward the west, their footwall and their outcrops toward the east, " are better to work than veins which extend from south to north, whose hangingwalls " are toward the east, and footwalls and outcrops toward the west. Although the latter " veins sometimes yield solid and good silver ore, still it is not sure and certain, because " the whole mineral force is completely scattered and dispersed through the outcrop, etc."