There is yet another argument. In many instances these circular-ended flints, when found upon the surface, have a comparatively fresh and unweathered appearance; and, what is more, have the chipped parts stained by iron-mould. In some cases there are particles of iron, in an oxidized condition, still adherent. Such iron marks, especially on flint which has weathered white, may, and indeed commonly do, arise from the passage of harrows |316| and other agricultural implements, and of horses shod with iron, over the fields; but did the marks arise merely from this cause, it appears hardly probable that in any instance they should be confined to the chipped edge, and not occur on other parts of the flint. [Illustration: Fig. 223.—Rudstone.] I had written most of the foregoing remarks when, in November, 1870, an interesting discovery, made by Canon Greenwell, F.R.S., in his exploration of a barrow[1427] at Rudstone, near Bridlington, in Yorkshire, came to corroborate my views. I have already described a whetstone found with one of the interments in this barrow, and mentioned that between the knees and the head were found, with other objects, the half of a nodule of iron pyrites, and a long round-ended flake of flint which lay underneath it. They are both represented full size in accompanying figure (Fig. 223). A portion of the outside of the pyrites has been ground smooth, and a projecting knob has been worked down, so as to bring it to an approximately hemispherical shape, and adapt it for being comfortably held in the hand. The fractured surface, where the nodule was broken in two, is somewhat oval, and in the centre, in the direction of the longer diameter, is worn a wide shallow groove, of just the same character as would have been produced by constant sharp scraping blows from a round-ended flake or scraper, such as that which was found with it. The whole surface is somewhat worn and striated, in the same direction as the principal central groove; and the edge of the flat face of the pyrites is more worn away at the top and bottom of the groove than at the other parts.