Rough stones, which have probably been used for triturating purposes, for the grinding of corn, etc., are occasionally found. In the Derbyshire barrows, for instance, portions of rubbed stones, and also of rubbers, have now and then been discovered. Two triturating stones, belonging to a different period, are given, for purposes of comparison, on figs. 143 and 144.[30] Whetstones, spindle-whorls, and other objects of stone, are also occasionally found. One of these spindle-whorls is shown on fig. 145. [Illustration: Fig. 145.] FLINTS, _i.e._, various instruments formed of flint, are undoubtedly the most abundant of any relics of the Ancient Britons found in or about grave-mounds. They are extremely varied in form, and many of them are of the most exquisite workmanship--such, indeed, as would completely baffle the skill, great though that skill undoubtedly is, of “Flint Jack”[31] to copy. The arrangement, classification, and nomenclature of flints is at present so uncertain, and so mixed up with absurd theories, that it is difficult to know how to place them in a common-sense manner. All I shall attempt to do in my present work--which is intended to describe, generally, the relics to be found in the barrows of the period, and not to be a disquisition on flints alone--will be to give examples of some of the more usual forms which have from time to time been found, so as to facilitate comparisons with those of various districts and countries. Of barbed arrow-heads, the examples here given will be sufficient to show the variety of forms and sizes which are usually found. The three first examples are from Green-Low, and are in the Bateman museum; the next three (figs. 149, 150, and 151) are also from Derbyshire examples in my own collection; fig. 152 is also from my own collection, but of a totally different form, approaching to the next example, fig. 153, which is in the museum of the Royal Irish Academy. Fig. 149 will be noticed to be peculiarly elegant in form, and marvellously delicate in manufacture--the barbs being extremely sharp and clearly defined. It is engraved of its full size, as are most of the other examples. Fig. 150 measures two and five-eighths inches in length. [Illustration: Fig. 146.] [Illustration: Fig. 147.] [Illustration: Fig. 148.] [Illustration: Fig. 149.] [Illustration: Fig. 150.] [Illustration: Fig. 151.] [Illustration: Fig. 152.] [Illustration: Fig. 153.] [Illustration: Fig. 154.]