BOOK V. 



147 



not yet pierced between the miners who on opposite sides are digging on 

 the same vein, or cross-stringers, or two veins which are approaching one 

 another. 



But 1 return to uur mines. If the surveyor desires to fix the boundaries 

 of the mecr within the tunnels or drifts, and mark to them with a sign cut in the 

 rock, in the same way that tiie Bergmcisler has marked these boundaries 

 above ground, he first of all ascertains, by measuring in the manner 

 which I have explained above, which part of the tunnel or drift lies 

 beneath the surface boundary mark, stretching the cords along the drifts to 

 a point beyond that spot in the rock where he judges the mark should be 

 cut. Then, after the same cords have been laid out on the surveyor's field, 

 he starts from that upper cord at a point which shows the boundary mark, 

 and stretches another cross-cord straight downward according to the sixth 



A — Needle of the instrument. B — Its tongue. C, D, E — Holes in the tongue. 



