nterest on account of the twinning
and the beautiful development of its crystals. It was first mentioned by
Philip Rashleigh in 1797 as "an ore of antimony," and was more
completely described by the comte de Bournon in 1804, after whom it was
named: the name given by Bournon himself (in 1813) was endellione, since
used in the form endellionite, after the locality in Cornwall where the
mineral was first found. The crystals are orthorhombic, and are
generally tabular in habit owing to the predominance of the basal
pinacoid (c); numerous smooth bright faces are often developed on the
edges and corners of the crystals. An un-twinned crystal is represented
in fig. 1. Usually, however, the crystals are twinned, the twin-plane
being a face of the prism (m); the angle between the faces of this prism
being nearly a right angle (86 deg. 20'), the twinning gives rise to
cruciform groups (fig. 2), and when it is often repeated the group has
the appearance of a cog-wheel, hence the name _Radelerz_ (wheel-ore) of
the Kapnik miners. The repeated twinning gives rise to twin-lamellae,
which may be detected on the fractured surfaces, even of the massive
material. The mineral is opaque, and has a brilliant metallic lustre
with a lead-grey colour. The hardness is 2-1/2, and the specific gravity
5.8.

[Illustration: FIG. 1.--Crystal of Bournonite.]

[Illustration: FIG. 2.--Twinned Crystal of Bournonite.]

At the original locality, Wheal Boys in the parish of Endellion in
Cornwall, it was found associated with jamesonite, blende and chalybite.
Later, still better crystals were found in another Cornish mine, namely,
Herodsfoot mine near Liskeard, which was worked for argentiferous
galena. Fine crystals of large size have been found with quartz and
chalybite in the mines at Neudorf in the Harz, and with blende and
tetrahedrite at Kapnik-Banya near Nagy-Banya in Hungary. A few other
localities are known for this mineral. (L. J. S.)

BOURREE, a French name for a dance common in Auvergne and in Biscay in
Spain; also a term for a musical composition or a dance-movement in a
suite, somewhat akin to the gavotte, in quick time with two beats to the
bar.

BOURRIENNE, LOUIS ANTOINE FAUVELET DE (1769-1834), French diplomatist,
was born at Sens on the 9th of July 1769. He was educated at the
military school of Brienne in Champagne along with Napoleon Bonaparte;
and although the solitary habits of the latter made intimacy difficult,