But, besides the mode of chipping out the shaft-hole in |47| perforated implements, several other methods were employed, especially in the days when the use of bronze was known, to which period most of the highly-finished perforated axes found in this country are to be referred. In some cases it would appear that, after chipping out a recess so as to form a guide for the boring tool, the perforation was effected by giving a rotatory motion, either constant or intermittent, to the tool. I have, indeed, seen some specimens in which, from the marks visible in the hole, I am inclined to think a metallic drill was used. But whether, where metal was not employed, and no central core, as subsequently mentioned, was left in the hole, the boring tool was of flint, and acted like a drill, or whether it was a round stone used in conjunction with sand, as suggested by the late Sir Daniel Wilson[145] and Sir W. Wilde,[146] so that the hole was actually ground away, it is impossible to say. I have never seen any flint tools that could unhesitatingly be referred to this use; but Herr Grewingk, in his “Steinalter der Ostseeprovinzen,”[147] mentions several implements in the form of truncated cones, which he regards as boring-tools (_Bohrstempel_), used for perforating stone axes and hammers. He suggests the employment of a drill-bow to make them revolve, and thinks that, in some cases, the boring tools were fixed, and the axe itself caused to revolve. Not having seen the specimens, I cannot pronounce upon them; but the fact that several of these conical pieces show signs of fracture at the base, and that they are all of the same kinds of stone (diorite, augite, porphyry, and syenite) as those of which the stone axes of the district are made, is suggestive of their being merely the cores, resulting from boring with a tube, in the manner about to be described, in some cases from each face of the axe, and in others where the base of the cone is smooth, from one face only. One of these central cores found in Lithuania is figured by Mortillet,[148] and is regarded by him as being probably the result of boring by means of a metal tube; others, from Switzerland, presumably of the Stone Age, are cited by Keller.[149] Bellucci[150] thinks that he has found them in Northern Italy. Worsaae[151] has suggested that in early times the boring may have been effected with a pointed stick and sand and water; and, |48| indeed, if any grinding process was used, it is a question whether some softer substance, such as wood, in which the sand or abrasive material could become imbedded, would not be more effective than flint. By way of experiment I bored a hole through the Swiss hatchet of steatite before mentioned, and I found that in that case a flint flake could be used as a sort of drill; but that for grinding, a stick of elder was superior to both flint and bone, inasmuch as it formed a better bed for the sand.