546 FAULTS INTERSECT METALLIC VEINS. 
versely, and its once continuous portions are 
thrown to a considerable distance from each 
other. This line of fracture is usually marked 
by a wall of clay, formed probably by the abra- 
sion of the rocks whose adjacent portions have 
been thus dislocated. Such faults are known in 
the mines of Cornwall by the term Jliican, and 
they often produce a similar advantage to those 
that traverse the Coal measures, in guarding the 
miner from inundation, by a series of natural 
dams traversing the rocks in various directions, 
and intercepting all communication between that 
mass in which he is conducting his operations, 
and the adjacent masses on the other side of the 
flucan or dam.* 
It may be added also, that the Faults in a Coal 
field, by interrupting the continuity of the beds 
of coal, and causing their truncated edges to abut 
against those of uninflammable strata of shale or 
* (( 
My object is rather to suggest whether the arrangement 
of veins, &c. does not argue design and a probable connection 
with other phenomena of our Globe. 
" Metalliferous veins, and those of quartz, &c. appear to be 
channels for the circulation of the subterraneous water and 
vapour ; and the innumerable clay veins, or '' flucan courses " 
(as they are termed in Cornwall), which intersect them, and are 
often found contained in them, being generally impervious to 
water, prevent their draining the surface of the higher grounds 
as they otherwise would, and also facilitate the working of mines 
to a much greater depth than would be practicable without 
them." R. W. Fox on the Mines of Cornwall, Phil. Trans. 
1830, p. 404. 
