148 
AMERICAN GEOLOGY. 
mass gently inclining to the north; this mass was about a hun¬ 
dred feet long and forty wide. It was all quarried out, and 
when this was done, the miners lost all trace of its direction. 
Several shafts were sunk in hopes of striking some parts of the 
mass or veins which it was supposed might be prolonged be¬ 
neath and between the lamina of the rock. These were all 
unsuccessful. The following diagram illustrates the relation of 
the vein to the rock, fig. 36, a, a, a, a, masses of ore, a is the 
Fig. 36. 
large mass already referred to. These five masses are regarded 
as parts of one vein, interrupted and broken at the time of up¬ 
heaval, presenting a very imperfect anticlinal axis. The mass 
a forms the crown, but being unsymmetrical and the others 
being lean their true relations had been overlooked. The 
dip on one side is to the east, and on the other to the 
west. The plan proposed for recovering the mine or vein 
was to tunnel from the eastern slope with a view of intersecting 
it, two hundred feet below the surface. The plan was adopted 
and the vein recovered. The complication was increased by 
numerous trap dykes. No less than seven crossed the mining 
tract in about two hundred feet. In diagram 37 the dykes and 
1 2 3 4 5 Dykei, A B C d Parts of the Vein. 
