ON THE LEAD MINING DISTRICTS OF YORKSHIRE. 169 
At the Cononley Mine in Airedale, the vein is frequently found to vary 
from an inch or two in width, to five or six yards, and that, within a longitu- 
dinal distance of a few feet. The width of a vein varies also with a change 
of strata; it is much greater in the hard strata, where it has a more erect 
position than in the soft ; it is generally more open in the Limestone than in 
the Gritstone, and very much contracted in the plate or shale. Frequently 
we find the vein to be 4 or 5 feet wide in the Grit or the Limestone, when 
it is scarcely perceptible in the plate. 
The beginning or termination of a vein longitudinally, is seldom explored ; 
where this has been done, the vein is found to ramify at acute angles, and 
_ the branches quickly terminate. 
A remarkable instance of this recently occurred at the Grassington Mines. 
In these mines, three levels were being driven eastward on the Cavendish 
Vein, at the respective depths of 20,37, and 50 fathoms from the surface. 
The 20-fathom level was in a stratum, locally known as the ‘ Top Grit ;’ the 
37 in the ‘ Bearing or Main Grit; and the 50-fathom level in the Limestone. 
Each level was at the time yielding from 6 to 9 tons of rich lead ore from 
every fathom driven. Many parties who went underground in this mine, after 
some length of such rich ground had been explored, and while the levels 
continued to yield at that rate, concluded that ground was being laid open 
from which immense profits could be made, for many years to come; and 
they were correct, so far as they had an opportunity of judging ; for, had 
the levels continued to open out such rich ground, no difficulty would have 
been found in making a profit of 40,0000. or 50,000/. a year from these mines. 
Unfortunately a change soon took place. The first cause for apprehen- 
sion noticed, was the wedge-like point of thin beds of Plate, introduced in 
_ different parts of the “‘ Bearing Grit,” in the 37-fathom level. As these became 
_ more numerous, and of greater thickness, the vein began to throw off 
 brauches on either side, and in the course of a few fathoms there was not a 
trace of the vein to be seen. As the upper and lower levels (the 20 and 
50) approached the same perpendicular point eastward, the vein in each case 
ramified into numerous strings. First, one branch was followed, and then 
another, until they disappeared entirely. At about 60 fathoms eastwards 
from where all trace of this vein was thus lost, a “ Crosscut” (that is, a level at 
right angles to the general bearing of the veins) was driven to some consi- 
derable distance both North and South of where it should have been inter- 
sected, had it continued eastward; but without discovering the slightest 
symptom of a vein. 
The Rake Veins are generally found to be “ Fault Veins.” Asa rule, the 
‘strata are lower on that side to which a vein hades or inclines, called the 
hanging wall, than on the one upon which it rests, known as the footwall 
of the vein. Thus a vein with the beds on the north side thrown up, will 
hade or underlie to the south. (See figs. 4 & 5.) 
The extent of the throw, or difference of level of the corresponding 
Strata, varies from a few inches to 20 or 30 fathoms; and such a difference 
is often met with when veins are in the immediate vicinity of each other. 
‘The extent of the throw is generally considered to denote the strength of 
the vein. A vein with a difference in the level of the strata of from 6 to 
18 feet, is regarded by the miner with more favour than one with a greater 
or less throw. Such a throw is considered evidence of sufficient strength of 
vein to ensure its continuity at a moderate size, and not such as to destroy 
the effect which certain beds are supposed to produce, when they are found 
in the same horizontal line, on each side of the vein. 
Am rocks of a different character are brought into the same horizontal 
—:1858. N 
