ipal heaths in the south of England, but is
specially abundant in the Highlands of Scotland.

[Illustration: Blackcock. ]

BLACK COUNTRY, THE, a name commonly applied to a district lying
principally in S. Staffordshire, but extending into Worcestershire and
Warwickshire, England. This is one of the chief manufacturing centres in
the United Kingdom, and the name arises from the effect of numerous
collieries and furnaces, which darken the face of the district, the
buildings and the atmosphere. Coal, ironstone and clay are mined in
close proximity, and every sort of iron and steel goods is produced. The
district extends 15 m. N.W. from Birmingham, and includes Smethwick,
West Bromwich, Dudley, Oldbury, Sedgley, Tipton, Bilston, Wednesbury,
Wolverhampton and Walsall as its most important centres. The ceaseless
activity of the Black Country is most readily realized when it is
traversed, or viewed from such an elevation as Dudley Castle Hill, at
night, when the glare of furnaces appears in every direction. The
district is served by numerous branches of the Great Western, London &
North Western, and Midland railways, and is intersected by canals, which
carry a heavy traffic, and in some places are made to surmount physical
obstacles with remarkable engineering skill, as in the case of the
Castle Hill tunnels at Dudley. Among the numerous branches of industry
there are several characteristic of certain individual centres. Thus,
locks are a specialty at Wolverhampton and Willenhall, and keys at
Wednesfield; horses' bits, harness-fittings and saddlery at Walsall and
Bloxwich, anchors and cables at Tipton, glass at Smethwick, and nails
and chains at Cradley.

BLACK DROP, in astronomy, an apparent distortion of the planet Mercury
or Venus at the time of internal contact with the limb of the sun at the
beginning or end of a transit. It has been in the past a source of much
perplexity to observers of transits, but is now understood to be a
result of irradiation, produced by the atmosphere or by the aberration
of the telescope.

BLACKFOOT (_Siksika_), a tribe and confederacy of North American Indians
of Algonquian stock. The name is explained as an allusion to their
leggings being observed by the whites to have become blackened by
marching over the freshly burned prairie. Their range was around the
headwaters of the Missouri, from the Yellowstone northward to the North
Saskatchewan and westward to the Rockies. Th