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 Subsolanus (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 Subsolanus 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.
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.
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.
