660 
south side down to such an extent as to cause plate to be 
opposed to gritstone, plate to limestone, and gritstone to 
limestone, and so on throughout the whole depth explored 
on them. Thus circumstanced, one of these veins yielded 
great quantities of ore, whilst its neighbour proved totally 
barren. 
Generally, when a vein occasions a throw of two or 
three fathoms, the ore neither continues above nor below the 
change of strata, but is confined to that part of the vein 
bounded by the bearing rock. This, however, has an 
exception in a vein at the mines before mentioned, which 
is at present producing large quantities of galena. In 
addition to affecting the fault or throw, rake veins, 
likewise, in most cases act " locally" on the "dip" of the 
strata, gradually bending the planes of stratification of the 
elevated beds, (for a short distance from the vein), 
downwards ; while in like manner they draw those of the 
depressed strata upwards. 
In each of our lead bearing districts the strata consist 
of numerous alternating beds of plate, grit, and lime- 
stone, forming the Yoredale rocks of Professor Phillips. 
Though the veins are found to traverse all these beds, it 
is only (generally speaking), in certain ones that lead ores 
are found ; limestone being the prevalently productive strata 
in some districts ; while in others the principal yield is from 
the gritstone. The argillaceous plates seldom produce ore, 
but even this admits of exception ; and the Cononley mine, 
in Airedale, (where the alternations of thick plates with 
their gritstones are exceedingly numerous,) has yielded 
continuous bunches of ore from the surface to a depth of 
thirty fathoms. From these facts it will be noted, that 
in mining for metallic minerals in this formation, we are 
not justified in the application of any but general rules; 
and that these admit of great variation in each district. 
