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THE OLD RED SANDSTONE.

this comparatively modern formation in this part of the worldere the line of wedges were forced through from below ? Awedge struck through the ice of a pond towards the centrebreaks its continuity, and we find the ice on both sides thewedge; whereas, when struck through at the pond edge, itmerely raises the ice from the bank, and we find it, in con-sequence, on but one side the wedge. Whether, have I ofteninquired, were the granitic wedges of this line forced throughthe Lias at one of its edges, or at a comparatively centralpoint 1 and about ten years ago I set myself to ascertainwhether I could not solve the question. The Southern Sutoris a wedge open to examination on both its sides : the MorayFrith washes it upon one side,—the Cromarty Frith on theother. Was the Lias to be found on both its sides 1 If so,the wedge must have been forced through the formation,—notmerely beside it. It occurs, as I have said, on the MorayFrith side of the wedge ; and I resolved on carefully explor-ing the Frith of Cromarty, to try whether it did not occuron that side too.

With this object I set out on an exploratory excursion, ona delightful morning of August 1830. The tide was falling,—it had already reached the line of half-ebb; and from theSouthern Sutor to the low long promontory on which thetown of Cromarty is built there extended a broad belt ofmingled sand-banks and pools, accumulations of boulders andshingle, and large tracts darkened with algae. I passed di-rect by a grassy pathway to the Sutor,—the granitic spear-head of a late illustration; and turned, when I reached thecurved and contorted gneiss, to trace through the broad beltleft by the retiring waters, and in a line parallel to what Ihave described as the shaft of the huge spear,—the beds andstrata of the Old Fed Sandstone in their ascending succes-sion. I first crossed the conglomerate base of the system,here little more than a hundred feet in thickness. The cease-