TE´REBRA
TE´REBRA (
τρύπανον,
τρυπάνιον,
τέρετρον), any instrument for boring wood, stone, or metal. Pliny
gives Daedalus as the traditional inventor (
H. N. 7.198; cf.
SERRA). We find a distinction
between
terebra antiqua, which produced dust
(
scobis), and
terebra
gallica, which produced
ramenta
or shavings (
Plin. Nat. 17.116;
Col. 4.29,
15 and 16).
The definition is not very clear: some have imagined that the
antiqua was a simple gimlet, and the
gallica a centre-bit, of which implement an, ancient
specimen is preserved in the Zürich Museum (see Blümner,
Techn. ii. fig. 43, i): the iron part, which alone
remains, is like that of a modern centre-bit. A centre-bit, however, would
not be a convenient tool for boring a tree in order to graft; and moreover
the fact that both Pliny and Columella give as a further distinction of the
gallica that it does not, like the other
kind, generate heat in boring, suggests that the
antiqua was a drill-borer, in principle like that described in
the Odyssey (see below), and the
gallica a
gimlet with a large spiral. It may be added that we should expect the simple
pointed drill, worked as Homer describes it, to be an earlier contrivance
than a borer with a spiral, which implies more advanced art both in the
inventor and the maker. Blümner suggests that the
τρύπανον and
τέρετρον correspond respectively to the
terebra antiqua and
terebra
gallica; but the definition in
Etym. Mag. makes the
τέρετρον merely a smaller
τρύπανον.
We find on monuments one kind of terebra exactly like our gimlet: another
kind in common use (and probably the older “invention of
Daedalus” ) was the “how-drill,” a borer twirled round
by means of a bow, the string of which was twisted round the handle of the
drill. This contrivance lasted till modern times, but has now, we believe,
been universally superseded by the “brace” or bent handle. In
the cut on page 243 both parts of the bow-drill are shown separately; the
compasses (
circini) lie between them. The
shipwright's borer mentioned in
Od. 9.384,
Eur. Cycl. 460, was similar in
principle, but on a larger scale. In these passages it is described by the
general term
τρυπανον: it had also a
specific name
ἀρίς (
Anth.
Pal. 6.103; Poll. 8.113). The wooden holder for the iron part of the
terebra was called
vagina (
Plin. Nat. 16.230). More references and
several figures from ancient representations of boring implements will be
found in Blümner,
Technologie, ii. pp. 223-226.
[
G.E.M]
