DYKES, MINERAL VEINS, &c. 79 
metamorphic shale, for trap, and suppose the latter to rest on limestone. 
The true series is as follows, proceeding downwards ; (Diag. No. 12.) 
a Basalt, rudely prismatic, gray with lichen, 
b Thin plate, not very much indurated. 
c Bed of plate, suhprismatic, 
d Beds of plate, laminated. 
e Thin limestone bed, with a superficial layer of pyrites. 
f Bed of hard pyritous limestone. 
xr Several beds of common dark limestone, with white shells and corals. 
CT 
The limestone here seen below the Whin, does not present any 
remarkable characters implying the action of heat, (unless we except 
the pyritous layer at top), but in the grand precipice of White force, 
the limestone which supports the trap, and is in contact with it, is 
converted to granular limestone, and plate is greatly indurated. 
The beds above the Whin sill are also locally much changed in struc- 
ture, texture, and aspect. The effects of heat are in some places more 
traceable above the Whin than under it; but they are no where 
important unless the mass of whin be considerable, Pelow Winch 
bridge, the Whin is thin, and limestone lying over it, (Tyne bottom 
limestone of Forster), is only partially affected. About half a mile 
below Winch bridge, I found plates alternating with three limestones ; 
the lower one was black within, and compact, the middle one was 
black and granular, both rather prismatized, the upper one blue, and 
partially pyritous ; Professor Sedgwick found, near this locality, more 
decided effects of heat. (Camb. Trans. Vol. II, p, 171.) 
The limestone lying above the Whin, in a circle round Caldron 
snout, is greatly changed from its usual aspect. The Tyne bottom 
limestone alluded to is, in this district, generally of a dark blue or 
blackish colour, and close texture, occasionally, however, containing 
crinoidal fragments and columns. On Widdybank scar, which seems 
about the point of maximum thickness of the Whin, this limestone is a 
