134 



THE GEOLOGIST. 



friability, or softness. The upper beds are the well-known and beautiful Purbeck 

 marble • beneath this, the thick beds of the harder kinds are adapted to sea-walls, 

 fortifications, and other soUd work, where minute cutting and rubbing are not 

 required. The more easily worked, or ' freestone beds,' are used for all kinds of 

 architectural dressings, external and internal stone-fittings, sunk and rounded 

 work, such as sinks, troughs, granary and rick-leg and cap-stones, and in fact all 

 those purposes where easy and clean cutting in work, and subsequent durability, 

 are essential. The thin beds are employed for paving, and the stone when well 

 selected is the best in the kingdom ; the very thin layers of tough limestone, or 

 the tough fissile beds, are split into suitable thicknesses as tilestones for roofing. 



" All the useful beds are broken up by natural partings into blocks and slabs of 

 various sizes, generally iiTegular rectangles, varying in size from ten or twelve 

 feet long, by five to eight feet wide, down to eight or fifteen inches long, by six or 

 ten inches wide, and three to eight inches thick. The latter class are termed 

 pitchers, the term ' horse pitchers ' being applied to the larger sizes. It is worthy 

 of remark, that amongst the useless beds, those called ^hones' by the workmen are 

 the most frequent. The name is exceedingly appropriate, as both in the original 

 mass, and in the smaller subdivisions, they have the smooth, rubbed appearance 

 of finished hones, or whetstones, as sold in shops. They are mostly argillaceous 

 or cherty hmestones, in their original mass appearing perfectly solid, without 

 any indication of partings, but on being handled continually subdivide into 

 rhombic pieces. But the most interesting to the stranger is the gTeat ' Cinder '-bed, 

 a blackish or brownish rock, with two or three subdivisions, consisting almost 

 wholly of a small oyster-shell, the Ostrea distort a, and so exceedingly hard and 

 intractable as to be almost useless, and only operated on by blasting. It would, 

 however, be very serviceable for marine works, or for exposed batteries. 



" The principal groups of beds of merchantable stone are termed veins by the 

 quarriers. Describing them in descending order, we meet first with the marble, for 

 ornamental purposes ; then the marhle-rag for walls ; and the lane-end, or laneing 

 vein beds, containing good stone for tomb-stones, paving, walling, and marine works. 

 Below this is the freestone-vein, a gToup containing kerb-, step-, and tile-stone, and 

 in its lower portion the admirably working and durable freestone, used for all kinds 

 of cut and hollow work as above described. Below this, immediately above the 

 great ^ cinder' -hed, is the dovms-vein series, worked almost wholly for paving. 

 Directly under the cinder is the feather-vein series, worked for steps, walls, and 

 marine" works, then below this the new-vein beds supply still larger slabs and 

 blocks, for similar pm-poses. 



" There is a freestone called Purleck bur, exceedingly durable, yet very free to 

 work, but the blocks are of small size. It was used for all the masonry of Corfe 

 Castle, and the wonderful sharpness of the work there at the present time, almost 

 without sign of decay, shows the value of the material. The quarries are not 

 regularly worked, and are situated near Orchard, in Knowle parish. It belongs 

 to the upper Purbeck strata. 



" The quanies are all worked undergi'ound, and entered by oblique shafts, from 

 twenty to a hundred feet deep ; a slope for di'agging up the stone, and steps at 

 the side for the workmen, with a rude capstan worked by a horse at the top, and 

 sheds adjoining, in which to cany on dressing the stone, constitute the whole 

 arrangements in these primitive works. There are in the Isle of Pm-beck about 

 one Innidred of these quarries, more than half being in the immediate neigh- 

 bourhood of Swanage ; it is difficult however to give the exact number, because 

 there are constantly some being abandoned, or new ones opened. 



" Below the true Purbecks is a great mass of clay-, sand-, and marl-beds, which 

 however thin out towards the sea-cliffs, so that there the Piu-beck limestones rest 

 at once on the crest of tlie tme upper oolite, or Portland limestone, and it is to 

 tlie stone obtained from this latter formation within the Purbeck district, that the 

 name of ^ Purhcck '' -Portland is given. In the essential quahties of closeness, 

 slight absorption, and durability, it excels the true ' Portland,' but these qualities, 

 characterisiim tlie oolite increasingly in an easterly direction, are also accompanied 

 by incroascHl hanhiess, so that the "fine quaiTies of Tilly Whim, and Howcombe, 

 near the eastern extremity of Purbeck, have been long disused for di'essed and 



