believe, of gault clay, which were some years ago bought up by the Great
Northern Railway in large numbers. These bricks have the peculiarity of
being pierced with holes about ½ in. in diameter, passing quite through
the brick, and they are extremely hard, partly because these holes
permit the hot air and smoke in the kiln to approach very near to the
interior of the brick. I am of opinion that the glazed or dull qualities
of hard bricks might with great advantage be often introduced into
London streets. What we want is something that will wash. The rough
surface of stocks or Suffolk facing bricks catches the black in the
London atmosphere and gradually gets dark and dull. A perfectly hard
face is washed clean by every shower. A good many years ago I built a
warehouse with stock bricks, and formed the arches, strings, etc., of
bricks with a very hard face, and, as I expected, the effect of time has
been to make these features stand out far better than when they were
fresh; in fact, the only question is whether they have not now become
too conspicuous. To return to the bricks in the London market: we have
firebricks made of fireclay, and almost vitrified and capable of
standing intense heat. These are used for lining furnaces, ovens, flues,
etc.

Then we have almost, if not quite, as refractory a material in
Staffordshire blue bricks, used--in various forms--for paving channels,
jambs of archways, etc. There are also small bricks called clinkers,
chiefly used for stable paving. Dutch clinkers, formerly imported
largely from Holland, were small, rough bricks, laid on edge, and
affording a good foothold for the horse. Adamantine clinkers, made of
gault clay, are much used; they must have chamfered edges, otherwise
they make too smooth a floor for a stable. Many other varieties are
obtainable in London, and are more or less used, but these are the most
prominent. In many parts of England special varieties of brick are to be