116 
SILUKIA. 
[Chap. VI. 
stone, of very irregular persistence. The ' ballstones ' (some of which 
near Wenlock have a diameter of 80 feet), being more crystalline than the 
nodules or ' bumbles,' have been quarried out as the best flux for the 
smelting of iron ; and their extraction has left caverns in the quarries, as 
shown in this woodcut. 
Old Quarries in the Wenlock Limestone. 
The dark cavities indicate the places from which the ' ballstones,' or best crystalline 
limestone, have been extracted. The fossils chiefly occur in the surrounding layers 
of impure earthy limestone and shale. 
But though very thick near Wenlock, this limestone thins out so rapidly 
in its range to the south-west, that even in the interior of the Ludlow pro- 
montory, as displayed in a diagram to be afterwards given, it is represented 
by thin courses made up of small concretions only ; and on the banks of the 
River Lugg, west of Aymestry*, it is merely represented by a few con- 
cretions, varying in size from 2 inches to 2 feet, but still full of beautiful 
and characteristic Corals. Thinning out entirely in Radnorshire, it is 
scarcely to be recognized throughout the counties of Brecon, Carmarthen, 
and Pembroke, its place being only marked in the eliffs of Marloes Bay, 
west of Milford Haven, by some fossils and a small quantity of impure 
limestone immersed in grey and sandy shale. 
In the districts of Malvern, Woolhope, May*Hill, and Usk, however, 
the Wenlock limestone is copiously and instructively developed ; and in 
numberless natural sections and quarries exhibits characters similar to 
those which it possesses in Shropshire. On the west flank of the Malverns, 
where in the Ridgeway of Eastnor Park it assumes the same linear out- 
line as at the Wenlock Edge, the limestone is estimated by Professor 
* In both of these localities the Wenlock lime- racteristic corals and other fossils figured in the 
stone was first traced by my friend the Kev. T. T. * Silurian System.' 
Lewis, who liberally gave to me many of the eha- 
