The large thin flat blades, usually subquadrangular or irregularly oval in form, of which a large number has been found in the Shetland Islands, and which are known as “Pech’s knives,” or “Picts’ knives,” apparently belong to the same class of instruments as the quadrangular and triangular tools lately described, and this would therefore appear to be the proper place for making mention of them. They are never formed of flint; the principal materials of which they are made being slate and compact greenstone, porphyry, and other felspathic rocks, and madreporite. Their usual length is from 6 inches to 9 inches, and the breadth from 3 inches to 5 inches; their thickness is rarely more than 1∕2 inch in the middle, and sometimes not more than 1∕10 of an inch. They are usually polished all over, and ground to an edge all round. Sometimes, however, the edge on one or more sides is rounded, and occasionally an end or side is left of the full thickness of the blade, and rounded as if for being held in the hand. I have a specimen, 4 1∕2 inches long, and 3 1∕4 inches wide at the base, formed of porphyritic greenstone, and found at Hillswick, in Shetland, which was given me by the late Mr. J. Gwyn Jeffreys, F.R.S. Its cutting edge may be described as forming nearly half of a pointed ellipse, of which the thick side for holding forms the conjugate diameter. This side is rounded and curved slightly inwards; one of the angles between this base and the elliptical edge is rounded, and a portion of the edge is also left thick and rounded, so that when the base is applied to the palm of the hand the lower part of the forefinger may rest upon it. When thus held it forms a cutting tool not unlike a leather-cutter’s knife. Instruments of this character are extremely rare in England, but in the extensive Greenwell Collection is a specimen which I have engraved as Fig. 261. It was found at Crambe, in the North Riding of Yorkshire, and is formed of an oolitic shelly limestone, a material also used for the manufacture of celts in |346| that district. Though smaller, and rather more deeply notched at the base than my Shetland knife, it is curiously like it in general form. The edge, however, only extends along one side, and is not carried round the point. [Illustration: Fig. 262.—Walls, Shetland. 1∕2]