The tools used were apparently of four kinds: a knife, a graver, a simple drill, and a tubular drill. The knife, perhaps of hardened bronze, was used for cutting the specimens of the softer materials into shape, while the graver, of flint or obsidian, was employed for cutting the device or inscription. Herodotus mentions[81] that the Ethiopians pointed their arrows with the same sort of hard stone or flint that was used for engraving signets. The simple drill, used for drilling the soft stone seals and for engraving those of the hard stone class, consisted of a metal drill with handle, the butt end of which revolved inside a stone or wooden cap which the engraver held in his hand, and was thus able to direct the point to the right place. The drill itself was made to revolve by means of rapidly moving forwards and backwards by a bow, the string of which was wound round the stick of the drill. Carpenters and cabinet workers in the East still use a similar bow drill at the present day. [Illustration: Fig. 16. WORKING THE BOW DRILL. (From the tomb of Rekhmara.)] The tubular drill was also worked in the same way with a bow, but instead of the drill being pointed as in the simple drill, it was tubular. With hard stones both these kinds of drill were used, with emery powder and oil or water. ------------------------------------------------------------------------ THE VARIETIES OF EGYPTIAN SEALS. [Sidenote: Varieties of Egyptian seals.] It has already been remarked that Egyptian seals may be divided into two great groups: namely (1) those of cylindrical shape, which were _rolled_ over the clay or other substance to be impressed; and (2) those with a flat base, which were used as _stamps_. Both these types probably originated in Western Asia. The first group comprises all (_a_) cylinder seals; to the second belong all (_b_) hemi-cylinder and cone shaped seals, (_c_) button shaped seals, (_d_) scarab shaped seals, (_e_) plaques and other miscellaneous forms, and (f) Signet rings. 1. CYLINDER SEALS. [Sidenote: Cylinder seals.]