variety of limestone properly called by this
name is almost confined to the Anglo-Parisian basin. Some chalk occurs
in the great Cretaceous deposits of Russia, and in Kansas, Iowa,
Nebraska and S. Dakota in the United States. Hard white chalk occurs in
Ireland in Antrim, and on the opposite shore of Scotland in Mull and
Morven.

_Economic Products of the Chalk._--Common chalk has been frequently used
for rough building purposes, but the more important building stones are
"Beer stone," from Beer Head in Devonshire, "Sutton stone" from a little
north of Beer, and the "Totternhoe stone." It is burned for lime, and
when mixed with some form of clay is used for the manufacture of cement;
chalk marl has been used alone for this purpose. As a manure, it has
been much used as a dressing for clayey land. Flints from the chalk are
used for road metal and concrete, and have been employed in building as
a facing for walls. Phosphatic nodules for manure have been worked from
the chloritic marl and Cambridge Greensand, and to some extent from the
Middle Chalk. The same material is worked at Ciply in Belgium and
Picardy in France. Chalk is employed in the manufacture of carbonate of
soda, in the preparation of carbon dioxide, and in many other chemical
processes; also for making paints, crayons and tooth-powder. _Whiting_
or _Spanish white_, used to polish glass and metal, is purified chalk
prepared by triturating common chalk with a large quantity of water,
which is then decanted and allowed to deposit the finely-divided
particles it holds in suspension.

_Chalk Scenery._--Where exposed at the surface, chalk produces rounded,
smooth, grass-covered hills as in the Downs of southern England and the
Wolds of Yorkshire and Lincolnshire. The hills are often intersected by
clean-cut dry valleys. It forms fine cliffs on the coast of Kent,
Yorkshire and Devonshire.

Chalk is employed medicinally as a very mild astringent either alone or
more usually with other astringents. It is more often used, however, for
a purely mechanical action, as in the preparation hydrargyrum cum creta.
As an antacid its use has been replaced by other drugs.

_Black chalk_ or _drawing slate_ is a soft carbonaceous schist, which
gives a black streak, so that it can be used for drawing or writing.
_Brown chalk_ is a kind of umber. _Red chalk_ or _reddle_ is an impure
earthy variety of haematite. _French chalk_ is a soft variety of
steatite, a hydrated magnesium