In this case the borer would appear to have somewhat resembled a centre-bit or pin-drill. In others[180] the holes are oval, and must have been much modified after they were first bored. The process of boring holes of large diameter in hard rocks such as diorite and basalt by means of tubes was in common use among the Egyptians. These tubes are supposed to have been made of bronze, and corundum to have been employed with them. Professor Flinders Petrie[181] has suggested that they had jewelled edges like the modern diamond crown drill, and that they could penetrate diorite at the rate of one inch in depth for 27 feet of forward motion. I think, however, that this is an over-estimate. Saws of the same kind were also used. Kirchner,[182] the ingenious but perverse author of “Thor’s Donnerkeil,” considers that steel boring tools must have been used |52| for the shaft-holes in stone axes; and even Nilsson,[183] who comments on the rarity of the axes with the central core in the holes, is inclined to refer them to the Iron Age. He[184] considers it an impossibility to bore “such holes” with a wooden pin and wet sand, and is no doubt right, if he means that a wooden pin would not leave a core standing in the centre of the hole. The drilling the holes through the handles of the New Zealand[185] _meres_ is stated to be a very slow process, but effected by means of a wetted stick dipped in emery powder. I have seen one in which the hole was unfinished, and was only represented by a conical depression on each face. In some stones, however, such holes can be readily bored with wood and sand; and in all cases where the stone to be worked upon can be scratched by sand, the boring by means of wood is possible, given sufficient time, and the patience of a savage. To what a degree this extends may be estimated by what Lafitau[186] says of the North American Indians sometimes spending their whole life in making a stone tomahawk without entirely finishing it; and by the years spent by members of tribes on the Rio Negro[187] in perforating cylinders of rock crystal, by twirling a flexible leaf-shoot of wild plantain between the hands, and thus grinding the hole with the aid of sand and water. The North American[188] tobacco-pipes of stone were more easily bored, but for them also a reed in conjunction with sand and water seems to have been employed. On the whole, we may conclude that the holes were bored in various manners, of which the principal were— 1. By chiselling, or picking with a sharp stone. 2. By grinding with a solid grinder, probably of wood. 3. By grinding with a tubular grinder, probably of ox-horn. 4. By drilling with a stone drill. 5. By drilling with a metallic drill. Holes produced by any of these means could, of course, receive their final polish by grinding.