Masonry

All work of this description must be executed in Portland ce ment, mortar of good strength, to avoid as much as possible the unequal settlement of the deep courses of stone facing and the narrower courses of the brick or rough stone backing. If the backing is of brick it should never be less than gin. thick, and whether of stone or brick it should be levelled up in courses of the same thickness as the ashlar.

Walling.—There are many different sorts of walling, or modes of structure, arising from the nature of the materials available in various localities. That is, perhaps, of most frequent occur rence in which either squared, broken or round flints are used. This, when executed with care, has a distinctly decorative appear ance. To give stability to the structure, lacing courses of tiles, bricks or dressed stones are introduced, and brick or stone piers are built at intervals, thus forming a flint panelled wall. The quoins, too, in this type of wall are formed in dressed stone or brickwork.

Uncoursed rubble built with irregular blocks of ragstone, as unstratified rock quarried in Kent, is in great favour for facing the external walls of churches and similar works.

Pointing.

As with brickwork this is generally done when the work is completed and before the scaffolding is removed. Suitable weather should be chosen, for if the weather be either frosty or too hot the pointing will suffer. The joints are raked out to a depth of half an inch or more, well wetted, and then refilled with a fine mortar composed specially to resist the action of the weather. This is finished flat or compressed with a special tool to a shaped joint, the usual forms of which are shown in fig. 5.

To give a uniform appearance to the stonework and preserve the finished face until a hard ened skin has formed, it is usual to coat the surface of exposed masonry with a protective com pound of ordinary limewhite with a little size mixed in it, or a spe cial mixture of stone-dust, lime, salt, whiting and size with a little ochre to tone it down. After six months or more the work is cleaned down with water and stiff bristle or wire brushes Some times muriatic acid much diluted with water is used.

Technical Terms.—Of the following technical terms, many will be found embodied in the drawing of a gable wall (fig. 6),

which shows the manner and position in which many different members are used.

Apex Stone.—The topmost stone of a gable forming a finial for the two sloping sides; it is also termed a "saddle" (fig. 6).

Blocking Course,

a heavy course of stone above a cornice to form a parapet and weigh down the back of the cornice (fig. 7).

Bed.—The bed surface upon which a stone is set or bedded should be worked truly level in every part. Many workmen to form a neat thin joint with a minimum amount of labour hollow the bed and thus when the stone is set all weight is thrown upon the edges with the frequent result that these are crushed.

Coping.—The coping or capping stones are placed on the top of walls not covered by a roof, spanning their entire width and throwing off the rain and snow, thus keeping the interior of the wall dry. The fewer the number of joints the better the security, and for this reason it is well to form copings with as long stones as possible. To throw water off clear, and prevent it from running down the face of the wall, the coping should project an inch or two on each side and have a throat worked on the underside of the projections (fig. 6).

Cornice,

a projecting course of moulded stone crowning a structure, forming a cap or finish and serving to throw any wet clear of the walls. A deep drip should always be worked in the upper members of a cornice to prevent the rain trickling down and disfiguring the moulding and the wall (fig. 7).

Corbel, a stone built into a wall and projecting to form a canti lever, supporting a load beyond the face of the wall.

Skew Corbel, a stone placed at the base of the sloping side of a gable wall to resist any sliding tendency of the sloping coping.

Stones placed for a similar purpose at intervals along the sloping side, tailing into the wall, are termed "kneelers" and have the section of the coping worked upon them.

Corbel Table, a line of small corbels placed at short distances apart supporting a parapet or arcade. This forms an ornamental feature which was much employed in early Gothic times. It prob ably originates from the machicolations of ancient fortresses.