For cleaning old stonework the sand blast operated either by steam or compressed air is used. Brick masonry is cleaned in the same manner as stone masonry. During the process of cleaning all open joints under window sills and elsewhere should be pointed.
Coping : The coping of a wall consists of large and heavy stones, slightly projecting over it at both sides, accurately bedded on the wall, and jointed to each other with cement mortar. Its use is to shelter the. mortar in the interior of the wall from the weather, and to protect by its weight the smaller stones below it from being knocked off or picked out. Coping stones Should he so shaped that water • may rapidly run off from them.
For coping stones the objections with regard to excess of length do not apply; this 'excess may, on the contrary, prove favorable, because, the number of top joints being thus diminished, the mass beneath the coping will be better protected.
Additional stability is given to a coping by so connecting the coping stones together that it is impossible to lift one of them without at the same time lifting the ends of the two next it. This is done either by means of iron cramps inserted into holes in the stone and fixed there with Icad, or, better. still, by means of dowels of wrought iron, cast iron, copper, or hard stone. The metal dowels are inferior in durability to those of hard stone, though superior in strength. Copper is strong and durable, but expensive. The stone dowels are small prismatic or cylindrical blocks, each of which fits into a pair of opposite holes in the contiguous ends of a pair of coping stones and fixed with cement mortar.
The under edge should be throated or dipped, that is, grooved, so that the drip will not run back on the wall, but droll from the edge. Coping is divided into three kinds.
Parallel coping, level on fop. Feather-edged coping, bedded lever and sloping feu top. Saddle-hack coping has a curved or doubly inclined top.
Corbell: A horizontal projecting' piece, or course, of masonry which assists in supporting one resting upon' it which projects still further. • Cornice : The ornamental projection at the eaves of a building or at the top of a pier or any other structure.
Counterfort: Vertical projections of stone or brick masonry built at intervals along the back of a wall to strengthen it, and gen erally of very little use.
Course : The term course is applied to each horizontal row or layer of stones or bricks in a wall; some of the courses have particular names, as: Plinth Course, a lower, projecting, square-faced course; also called the water table.
Blocking Course, laid on top of the cornice.
- Bonding Course, one in which the stones or bricks lie with their length across the wall; also called heading course.
Stretching Course, consisting of stretchers.
Springing Course, the course from which an arch springs. String Course, a projecting course.
' Rowlock Course, bricks set on edge.
Cramps: Bars of iron having the ends turned at right angles k) the. body of the bar, and inserted in holes and trenches cut in the upper sides of adjacent stones to hold them together (see Coping).
Cutwater or Starling : The projecting ends of a bridge pier, etc., usually so shaped as to allow water, ice, etc., to strike them with but little injury.
Dowels : Straight bars of iron, copper, or stone, which are placed in holes cut in the upper bed of one stone and in the lower bed of the next stone above. They are also placed horizontally in the adjacent ends of coping stones (see under Coping). Cramps and dowels arc fastened in place by pouring melted lead, sulphur, or cement grout around them.
Dry Stone Walls may be of any of the classes of masonry previously described, with the single exception that the mortar is omitted. They should be built according to the principles laid down for the class to which they belong.
Face : The front surface of the wall.
Facing: The stone which forms the face or outside of the wall exposed to view.
Footing : The projecting courses at the base of a wall for the purpose of distributing the weight over an increased area, and thereby diminishing the liability to vertical settlement from compression of the ground.