ts and straps, and sometimes of stone, but the
difficulty of properly fixing this latter material causes it to be
neglected in favour of one of the former. (See a paper by F.J. Bancroft on
"Chimney Construction," which contains a tabulated description of nearly
sixty shafts, _Proc. Civ. and Mech. Eng. Soc._, December 1883.)

The work of laying bricks or tiles as paving falls to the lot of the
bricklayer. Paving formed of ordinary bricks laid flat or on their
[Sidenote: Brick paving.] edges was once in general use, but is now almost
abandoned in favour of floors of special tiles or cement paving, the latter
being practically non-porous and therefore more sanitary and cleaner.
Special bricks of extremely hard texture are made for stable and similar
paving, having grooves worked on the face to assist drainage and afford
good foothold. A bed of concrete 6 in. thick is usually provided under
paving, or when the bricks are placed on edge the concrete for external
paving may be omitted and the bricks bedded in sand, the ground being
previously well rammed. The side joints of the bricks are grouted in with
lime or cement. Dutch clinkers are small, hard paving bricks burned at a
high temperature and of a light yellow colour; they are 6 in. long, 3 in.
wide, 11/2 in. thick. A variety of paving tile called "oven tiles" is of
similar material to the ordinary red brick, and in size is 10 or 12 in.
square and 1 to 2 in. thick. An immense variety of ornamental paving and
walling tiles is now manufactured of different colours, sizes and shapes,
and the use of these for lining sculleries, lavatories, bathrooms,
provision shops, &c., makes for cleanliness and improved sanitary
conditions. Besides, however, being put to these uses, tiles are often used
in the ornamentation of buildings, externally as well as internally.

Mosaic work is composed of small pieces of marble, stone, glass or pottery,
laid as paving or wall lining, usually in some ornamental pattern or
design. A firm bed of concrete is required, the pieces of [v.04 p.0528]
material being fixed in a float of cement about half or three-quarters of
an inch thick. Roman mosaic is formed with cubes of marble of various
colours pressed into the float. A less costly paving may be obtained by
strewing irregularly-shaped marble chips over the floated surface: these
are pressed into the cement with a plasterer's hand float, and the whole is
then rolled with an iron roller. This is called