Sometimes these hammer-heads are, in outline, of an intermediate form between Figs. 151 and 152, being oval in section, and more rounded at the smaller end than the larger, which is somewhat flattened. One such, in the Christy Collection, is formed of granite, and was found at Burns, near Keswick, Cumberland. Another, of quartzite, 3 1∕4 inches long, found on Breadsale Moor, is in the Museum at Derby. Neither of them presents the same high degree of finish as Fig. 151. They seem, indeed, to have been made from pebbles, which were but slightly modified in form by their conversion into hammer-heads. Occasionally, though rarely, flint pebbles naturally perforated have been used as hammers. In excavating a barrow at Thorverton,[794] near Exeter, the Rev. R. Kirwan discovered a flint pebble about 3 3∕4 inches long, with a natural perforation rather nearer one end than the other, but which on each face has been artificially enlarged. Each end of the pebble is considerably abraded by use. No other relics, with the |226| exception of charcoal, were found in the barrow. Mr. Kirwan suggests that the stone may have been used by placing the thumb and forefinger in each orifice of the aperture; but not improbably it may have been hafted. In the Museum at Copenhagen are one or two axes of flint, ground at the edge, but with the shaft-holes formed by natural perforations of the stone. And in M. Boucher de Perthes’ Collection[795] were two hammer-heads, with central holes of the same character. [Illustration: Fig. 153.—Maesmore, Corwen.]