Mr. Outram on the Discovery, &c. 351 
perforated about 24,0 yards in length from the entrance of the 
hill, and were about eighty yards deep from the surface of the 
ground immediately over them, when they discovered on the 
north side of their work a fault, throw , or break of the strata, 
which was filled with shale, reared on the edge, and mixed 
with softer earth, and in some places with small lumps of coal. 
In continuing to pursue the direction of the tunnel, this fault 
occupied by degrees more of the space of the tunnel, for about 
forty yards in length, when it nearly occupied the whole tun- 
nel, which is near four yards in width ; and at about five feet 
from its southern margin it contained a rib of limestone, near 
four feet thick in the bottom, but not quite so thick at the top 
of the tunnel ; and on each side this rib it contained balls of 
limestone promiscuously scattered, and of various sizes, from 
one ounce to upwards of loolbs. weight. 
The rib and balls of limestone were first found at about 280 
yards from the north-eastwardly end of the tunnel, where it 
is about go yards in perpendicular depth from the surface ; 
and the workmen have now pursued the tunnel to near 350 
yards from the entrance, and the rib of limestone and balls 
continue nearly the same ; the rib has varied a little in thick- 
ness, and has not pursued a straight line ; it in one place 
nearly left the tunnel to the northward, but in a few yards 
turned southward, to its former direction. The limestone of 
the rib is not perfectly pure, that in the balls is still less so, 
but it makes a good lime for cement. The balls when broken 
appear to be mixed with a kind of pyrites, in small particles, 
near their outward edges ; their form is very peculiar, being 
similar in all their sizes ; it is not perfectly globular, being flat- 
tened a little on two opposite sides, which appear to have been 
MDCCXCVI. Zz 
