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 found, and every here and there one falls upon a good brickmaker who is able to produce good moulded or embossed or ornamental bricks, such as those which have been supplied to me years ago by Mr. Gunton, and more recently by Mr. Brown, both of Norwich, or by Mr. Cooper, of Maidenhead.

It is of importance to those whose business it is to look after or engage in building operations, that they should early learn what to look out for in each material.  Of course, a man only becomes a judge of bricks, or timber, or stone by experience; but he is far better able to take the benefit of experience when it comes to him if he knows from the first to what points to direct attention.  Wherefore I make no apology for trying to put before you the points of a good brick, and in doing so I shall partly quote from a memorandum published now a good many years ago by the Manchester Society of Architects.