168 ~ > REPORT—1858. ~~ 
(as they are termed) of certain extent, defined by fixed boundaries, which 
has been practised in Devon and Cornwall from a very early period, is now 
almost generally adopted in this county. 
Generally speaking, the various lead mines which constitute such an im- 
portant portion of the mineral treasures of Great Britain, are situated on 
rugged and barren elevations, and in this respect those of Yorkshire are not 
exceptions. 
If we draw an imaginary line from I{kley, bearing about 12° West of 
North, for a distance of 35 miles, and then parallel ones to it, through points 
10 miles east and 10 miles west from the centre line, we shall in this area of 
700 square miles, include the high and uncultivated districts bounding 
Airedale, Wharfedale, Nidderdale, Wensleydale, Arkendale and Swaledale; 
in which I believe all the lead mines in this county, that have been or are 
being worked to any extent, are situated. 
The strata throughout the whole of this area, are (like those of the great 
lead-bearing districts of Northumberland, Cumberland, and Durham, and 
also of Derbyshire) the lower members of the Carboniferous Series. 
Although the same class of rocks prevails throughout our lead-bearing 
districts, we do not always find each individual stratum to occur, even in 
mines in the immediate vicinity of each other ; and when they do exist, their 
thickness is frequently found to vary considerably. 
It is therefore impossible to make a section, that would correspond with 
every mining district, or even hold good throughout a single mining field. 
Plate XVIII. figs. 1, 2, and 3, are sections of the strata sunk through in 
three of the shafts on the Grassington Mines in Wharfedale. From these it 
will be observed, that even in situations so close to each other, the thickness 
of the beds varies considerably. 
The greatest thickness of Limestone yet proved at Grassington is 66 yards, 
whereas at the Cockhill Mines, near Pateley Bridge, only about 6 miles _ 
distant, it is found to be at least 180 yards thick. 
In the metalliferous portion of the Carboniferous rocks, we have the 
Rake Vein, the Pipe or Tube Vein, and the lateral embedded, or Flat Vein. 
The first has the appearance of a rent or fissure in the strata, extending 
to a great length, and generally to an unknown depth. The second, or 
Pipe Vein, has the form of an irregular tube, is met with in certain strata, 
(generally Limestone), and dips with the beds, or passes more or less diago- 
nally through them, for a great length. The Flat Vein is seldom met with, 
except in connexion with some Rake Vein, but has always a position con- 
formable to the stratum in which it is embedded. 
The Rake Veins are by far the most numerous in every district, and the 
phenomena presented by them the most varied and complicated. The 
greater portion of our lead cre likewise is obtained from them. 
The longitudinal course, or “bearing,” of a Rake Vein, is seldom (if ever) 
a perfectly straight line; but, for the most part, it gives a tolerably direct 
bearing throughout its entire length. 
The downward course of these veins varies considerably in the angles 
formed with the vertical. The “ Hade,” or inclination, is likewise more toward 
a horizontal position, in the soft or Argillaceous Beds, than in the more hard 
and solid rocks; and sometimes in passing a seam of Coal or of soft Clay, it 
takes the direction of the stratum for a greater or less distance. (See figs. 
4, 5, and 6.) 
The width of the vein is not uniform throughout its whole length; it 
frequently opens out from a width of a foot or two, to one of as many yards, 
and then contracts until it becomes a mere thread or joint. 
