BOOK III. 



67 



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 spht 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. 



A, B — Veins dividing. C — The same joining. 



Whether a vein is separating from or uniting with another can be deter- 

 mined only from the seams in the rocks. For example, if a principal 

 vein nms from the east to the west, the rock seams descend in depth 

 likewise from the east toward the west, and the associated vein which 

 joins with the principal 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 principal vein — which remain 

 the same after the junction — unless the associated vein proceeds in the same 

 direction as the principal vein. In that case we name the broader vein the 

 principal one, and the narrower the associated vein. But if the principal 

 vein splits, the rock seams which belong respectively to the parts, keep 

 the same course when descending in depth as those of the principal vein. 



But enough of venae profundae, their junctions and divisions. Now 

 we come to venae dilatatae. A vena dilatata may either cross a vena profunda, 

 or join with it, or it may be cut by a vena profunda, and be divided into parts. 



