Direction of Strata. " $5 but if they differ not only in diredtion, but lie over the ends of the ftrata of the fundamental rock, they are fa id to be unconformable and over- lying. Overlying ftrata occur more frequently than fimply unconformable, and have far greater extent. 4. Direction of the Strata them/elves, without re« ference to the Fundamental Rock. Strata are either flraight, that is, difpofed in one direction on rtie fundamental rock . or they turn around it, and inclofe it; in this cafe they are faid to be mantle formed, or mantle-fhaped. If the ftrata are not only wrapped around the fundamental rock, but alfo cover its extremities, they are faid to be faddle-Jhaped. When the upper part of the faddte-fhape is car ried away, the mantle-Jhape is formed. ; Strata are fometimes concave, and they are then faid to be bafin-fiaped; but if the concavity be oblong, they are named trough-Jhapcd. In the concave, that is, the bafon and trough fhaped, and convex, that is, the faddle and mantle fhaped ftra ta, the outgoings * form circles : in the concave, Vol. III. I ‘ the * By the outgoings of the ftrata are undei flood their upper extremities as they appear at the furface of tho earth.
