68 



BOOK III. 



A, C — Vena dilalata crossing a vena profunda. B — Vena profunda. D, E — Vena 



dilatata which junctions with a vena profunda. F — Vena profunda. G — Vena dilatata. 



H, I — Its divided parts. K — Vena profunda which divides the vena dilatata. 



Finally, a vena profunda has a " beginning " (origo), an "end" {finis), a 

 "head" (caput), and a "tail" {cauda). That part whence it takes its rise 

 is said to be its " beginning," that in which it terminates the " end." Its 

 " head "* is that part which emerges into dayhght ; its " tail " that part 

 which is hidden in the earth. But miners have no need to seek the 

 " beginning " of veins, as formerly the kings of Egypt sought for the source 

 of the Nile, but it is enough for them to discover some other part of the vein 

 and to recognise it.^ direction, for seldom can either the " beginning " or the 

 " end " be found. The direction in which the head of the vein comes into 

 the light, or the direction toward which the tail extends, is indicated by its 

 footwall and hangingwall. The latter is said to hang, and the former to lie. 

 The vein rests on the footwall, and the hangingwall overhangs it ; thus, 

 when we descend a shaft, the part to which we turn the face is the foot- 

 wall and seat of the vein, that to which we turn the back is the hanging- 

 wall. Also in another way, the head accords with the footwall and the tail 

 with the hangingwall, for if the footwall is toward the south, the vein 

 extends its head into the light toward the south ; and the hangingwall, 

 because it is always opposite to the footwall, is then toward the north. 

 Consequently the vein extends its tail toward the north if it is an inclined 

 vena profunda. Similarly, we can determine with regard to east and west 

 and the subordinate and their intermediate directions. A vena profunda 

 which descends into the earth may be either vertical, inclined, or crooked : 

 the footwall of an inclined vein is easily distinguished from the hangingwall, 

 but it is not so with a vertical vein ; and again, the footwall of a crooked 

 vein is inverted and changed into the hangingwall, and contrariwise the 

 hangingwall is twisted into the footwall, but very many of these crooked 

 veins may be turned back to vertical or inclined ones. 



*It might be considered that the term " outcrop " could be used for " head," but it 

 will be noticed that a vena dilatata would thus be stated to have no outcrop. 



