BOOK V. 145 



of the drift or tunnel the raise should be made, and how many fathoms of 

 vein remain to be broken through in order that the shaft may be connected. 



I have described the first reason for surveying ; I will now describe 

 another. When one vein conies near another, and their owners are different 

 persons who have late come into possession, whether they drive a tunnel 

 or a drift, or sink a shaft, they may encroach, or seem to encroach, without 

 any lawful right, upon the boundaries of the older owners, for which reason 

 the latter very often seek redress, or take legal proceedings. The surveyor 

 either himself settles the dispute between the owners, or by his art gives 

 evidence to the judges for making their decision, that one shall not encroach 

 on the mine of the other. Thus, first of all he measures the mines of each 

 party with a basket rope and cords of linden bark ; and having applied to the 

 cords an orbis or a compass, he notes the directions in which they extend. 

 Then he stretches the cords on the surveyor's field ; and starting from that 

 point whose owners are in possession of the old meer toward the other, 

 whether it is in the hanging or footwall of the vein, he stretches a cross- 

 cord in a straight line, according to the sixth division of the compass, 

 that is, at a right angle to the vein, for a distance of three and a 

 half fathoms, and assigns to the older owners that which belongs to 

 them. But if both ends of one vein are being dug out in two tunnels, or 

 drifts from opposite directions, the surveyor first of all considers the lower 

 tunnel or drift and afterward the upper one, and judges how much each of 

 them has risen little by little. On each side strong men take in their hands 

 a stretched cord and hold it so that there is no point where it is not strained 

 tight ; on each side the surveyor supports the cord with a rod half a fathom 

 long, and stays the rod at the end with a short stick as often as he thinks 

 it necessary. But some fasten cords to the rods to make them steadier. 

 The surveyor attaches a suspended plummet level to the middle of the cord to 

 enable him to calculate more accurately on both sides, and from this he ascer- 

 tains whether one tunnel has risen more than another, or in like manner one 

 drift more than another. Afterward he measures the incline of the shafts 

 on both sides, so that he can estimate their position on each side. Then he 

 easily sees how many fathoms remain in the space which must be broken 

 through. But the grade of each tunnel, as I said, should rise one fathom in 

 the distance of one hundred fathoms. 



The Swiss surveyors, when they wish to measure tunnels driven into 

 the highest mountains, also use a rod half a fathom long, but composed of 

 three parts, which screw together, so that they may be shortened. They 

 use a cord made of linden bark to which are fastened slips of paper showing 

 the number of fathoms. They also employ an instrument peculiar to them, 

 which has a needle ; but in place of the waxed circles they carry in their 

 hands a chart on which they inscribe the readings of the instrument. The 

 instrument is placed on the back part of the rod so that the tongue, and the 

 extended cord which runs through the three holes in the tongue, demonstrates 

 the direction, and they note the number of fathoms. The tongue shows 

 whether the cord inclines forward or backward. The tongue does not hang, 



