25S Dr Traill on the Mineralogy of Halhin Mountain^ 
and is succeeded by thick beds of the same substance, (here 
named Chert or Chirh by the miners,) which continues to the 
depth of eighty-five yards more. The principal lead-veins in 
this mine are in the chert, and the shaft has only been sunk 
four yards in the limestone. The whole beds here generally 
dip one in three, but this is subject to considerable variation. 
This mine may be considered as unfolding the geological struc- 
ture of the eastern side of the mountain ; for it nearly corre- 
sponds with what has been observed along all this slope. As 
we ascend, however, the slaty-rock decreases in thickness, or 
gives place sooner to the solid beds of chert, and almost disap- 
pears on the summit. The shafts of two extensive mines on 
the summit are wrought by Lord Grosvenor, and go to great 
depths. The Old-Rahe mine near Halkin Hall has reached the 
depth of eight score yards. It has no steam-engine on it ; the 
ore is raised by well constructed horse-engines, and his Lord- 
ship’s engineers are now engaged in carrying a new level toward 
it from the lower part of the adjacent valley. This level com- 
mences at Nant-y-Flint : about 500 yards in length are already 
excavated, but when completed, it will extend about 1500 yards 
farther, and, at this point, will be 230 yards below the surface 
on the eastern slope of Halkin. The work is carried on day 
and night, yet it will still require several years for its comple- 
tion : its estimated cost is said to be L. 20,000. I may here 
remark, that some of the mines near Holywell are drained by a 
well constructed and judicious level, begun in 1774, and carried 
into the mountain for about 1200 yards. The Old-rake has 
been a most productive mine, and is still wrought with spirit. 
The other mine, called Lord Grosvenor’s Main, on the southern 
summit of Halkin, has also a deep shaft. The ore is here 
drawn up by a new double-stroke steam-engine, and the mine is 
pumped by a large Watt’s atmospheric engine. The depth of 
the shaft is nine score yards, and the effect of the general rise 
of the beds of Halkin mountain towards the west, is here appa- 
rent in the nearer approximation of the limestone to the surface. 
The first sixty yards are through the slaty rock and chert, but 
the rest of the shaft is driven through beds of a bluish-grey 
limestone. In this mine the principal metallic veins run east 
and west, but in the Old-rahe they lie north and south, which 
last Ixive been extremely rich, contrary to the prevailing opinion 
