DEPOSITED IN WATER. 
7 
parallel to the planes of cleavage. There is in some places a more 
frequent alternation of the finer and coarser varieties, and in such cases 
it is interesting to remark that the numerous cross quartz veins in the 
latter cease without penetrating the former. Certain cleavage planes 
are covered by arborescent films or cubical crystals of iron-pyrites 
imbedded by some of their square faces in a parallel coating of a 
fibrous zoolitic mineral, which occasionally softens by exposure into 
nacreous laminae. In some layers of slate, minute polyhedral crystals 
of pyrites are disseminated ; in others the spaces they occupied are 
filled by a black powder. — The slates are crossed by a set of secret 
parallel divisional planes called ‘ bate.’ In Clapham dale the slaty 
laminae range nearly east, and dip 60° S. In the valley of Wliarfe, 
besides a large quantity of granular rock, slate is seen in great abun, 
dance, under the level limestone, with laminae of cleavage directed 
E. S. E., and dipping 45° S. S. W. In Ribblesdale the slaty rocks are 
widely expanded, and are worked at many points for roofing, and 
flagging, and perhaps finer stone of the kind is no where known. It 
is quarried in a peculiar manner, with attention not only to the structure 
of the rock but also to the situation, and dryness ; for these circum- 
stances are found to have influence on the quality of the stone. Ill 
all the quarries hereabout, whether under the limestone scars, or in 
the midst of the slaty region, two constant sets of parallel divisional 
planes divide the whole rock into rhomboidal prisms, lying horizontally, 
and joints, vertical, oblique, and horizontal, truncate these prisms va- 
riously. (1) Of the two sets of planes, one called ‘ spires,’ by the 
workmen, is very obvious, and divides the rock into tables of great extent 
and uniform thickness, which are sometimes separated by a little soft 
greenish substance. (2) In one quarry the other scarcely visible planes 
called * bate,’ by the workmen, cross the spires at an angle of 51°, (39° on 
the ends of the tables,) and while they dip 71° N. N. E. and range 
E. S. E., these dip 70° S., and range nearly E. and W. The ‘ bate’ may 
be looked upon as the secret laminar structure of the stone, which is 
occasionally developed by weathering to an obvious degree. (3) Vertical 
joints called ‘ends,’ cross both spires and bate; and in the quarry 
Bow referred to they meet the spires at angles of 84° and 96° nearly. 
