ed
lime, the mixture is then slightly moistened with water and afterwards
moulded into bricks under powerful presses, capable of exerting a pressure
of about 60 tons per sq. in. After removal from the press the bricks are
immediately placed in huge steel cylinders usually 60 to 80 ft. long and
about 7 ft. in diameter, and are there subjected to the action of
high-pressure steam (120 lb to 150 lb per sq. in.) for from ten to fifteen
hours. The proportion of slaked lime to sand varies according to the nature
of the lime and the purity and character of the sand, one of lime to ten of
sand being a fair average. The following is an analysis of a typical German
sand-lime brick: silica (SiO_2), 84%; lime (CaO), 7%; alumina and oxide of
iron, 2%; water, magnesia and alkalis, 7%. Under the action of the
high-pressure steam the lime attacks the particles of sand, and a chemical
compound of water, lime and silica is produced which forms a strong bond
between the larger particles of sand. This bond of hydrated calcium
silicate is evidently different from, and of better type than, the filling
of calcium carbonate produced in the mortar-brick, and the sand-lime brick
is consequently much stronger than the ordinary mortar-brick, however the
latter may be made. The sand-lime brick is simple in manufacture, and with
reasonable care is of constant quality. It is usually of a light-grey
colour, but may be stained by the addition of suitable colouring oxides or
pigments unaffected by lime and the conditions of manufacture.

_Strength of Brick._--The following figures indicate the crushing load for
bricks of various types in tons per sq. in.:--

Common hand-made from 0.4 to 0.9
" machine-made " 0.9 " 1.2
London stock " 0.7 " 1.3
Staffordshire blue " 2.8 " 3.3
Sand-lime " 2.9 " 3.4

See also BRICKWORK.

(J. B.*; W. B.*)

[1] The term "marl" has been wrongly applied to many fire-clays. It should
be restricted to natural mixtures of clay and chalk such as those of the
Paris and London basins.

BRICKFIELDER, a term used in Australia for a hot scorching wind blowing
from the interior, where the sandy wastes, bare of vegetation in summer,
are intensely heated by the sun. This hot wind blows strongly, often for
several days at a time, defying all attempts to keep the dust down, and
parching all vegetation. It is in one sense a heal