TIN STOCKWOKKS IN CORNWALL. 655 



results ; and indeed I doubt whether there is any place in the world 

 where such poor tin-rock is being treated as at Wheal Prosper. 



Mulberry Mine, situated about 3| miles W.S.W. of Bodmin, and 

 1| mile N.W. of Wheal Prosper, is a large open quarry. The pit is 

 about 30 yards wide at the bottom and about 300 yards long from 

 north to south. Thirty yards, however, does not express the total 

 width of the tinny ground, as some is still left standing on the east 

 side of the pit. At the north end the pit is about 120 feet deep, 

 and 80 feet at the other. The killas, which is of an ash-grey colour, 

 dips at an angle of about 45° in a direction N. 22° W. (true). It is 



Pig. 1 . — Veins in Mulberry Mine. 

 w. e. 



Iiicli?3^;'- , s'' ,T J i 2 3Eeet 



traversed by numerous branches or veins running N. 7° W., dipping 

 about from 80° to 90° W., and varying from mere joints to veins 4 or 

 5 inches in width, rarely more than a foot apart, in fact generally only 

 a few inches. Many of the veins preserve their independence for a 

 considerable distance without intersecting other branches ; but at the 

 same time it is easy to find junctions both in the dip and in strike ; 

 sometimes also two adjacent strings may be connected by a " floor" 

 or vein of tin following the stratification. In addition to oxide of 

 tin the veins contain quartz and a little arsenical pyrites and wolf- 

 ram. 



The appearance of the N. end of the quarry will be readily un- 

 derstood by reference to figure 1, whilst a second diagram (fig. 2) 

 shows the general mode of working. 



Men, standing at A, bore and blast holes, which throw the rock 

 to B, under which a level has been driven with an opening C, usually 

 closed by a hatch. A waggon is run in, and by opening the hatch 

 it is filled without labour. As the face of the quarry gets further 

 and further north from the removal of a succession of more or less 

 vertical slices, the little level is driven on ahead and another hatch 

 made. 



Q.J. G.S. No. 135. 2x 



