concrete, which is now usually employed, the usual depth would be the longest dimension. Where we excavate and find a water-level, it is advisable to fill up that portion of the excavation up to that level with broken bricks. The actual composition of the concrete is usually 6-1 of Portland cement and Bolt Wood Tubes Concrete CI Washer nut ballast, the latter being composed of 2-1 of 1-in. broken stone and sand. This is laid and rammed in 4-in. layers to within 1 in. of top level. It should then be covered with damp sacks and left for 30 hours at least. When a rendering 1 in. thick of 1-1 P.C. and sand is applied the whole is smoothed off and left for 6 or 8 days. In boggy ground a load of 6-8 cwt. per ft.-super is ample. The depth, however, for economy may be considerably reduced, but if this is carried to an extreme it may be necessary to apply reinforcing bars of small H section placed longitudinally and transversely. It is customary to make a wooden templet of the engine. bed, with the exact position of the foundation bolts This is placed in position and the masonry or brickwork built round it The verticals are light trucks, in which the foundation bolts are eventually placed. These bolts have a shoe at their lower end, which is well embedded in the masonry or concrete. FIG. 242A. Holding-down bolts must never be cemented into position. Gas pipe is frequently used in place of the wood vertical tubes. A foundation bolt is shown in fig. 242A. CHAPTER XV. BRICKWORK AND MASONRY. ALTHOUGH the subject of brickwork and masonry belongs more to elementary treatises on Building Construction than to a book of this class, yet it would seem to be incomplete unless a few words were said on the more important points of the subject, especially as to the heavier classes of masonry which fall into the hands of the engineer, such as dock walls, etc. Brickwork.-As probably the reader is aware, brickwork is divided into two classes of what are termed "bond," that is, English and Flemish. There Header Elevation Elevation Plan on Course X English Bond FIGS. 243 and 244. are others, all more or less of a fancy nature. Plan on Course X Flemish Bond FIGS. 245 and 246. For general strength and stability in structures, nothing can compare with the English bond, of which an example is given in figs. 243 and 244. Here we have alternate courses of headers and stretchers, with what we call a closer in every alternate course to get the bond. The average brick (their composition was described under Materials of Construction) measures 9" x 4" x 3", a size which includes one mortar joint. They are laid in courses 3 in. deep. The joints between the courses are the bed joints, the corner bricks are the quoins. The vertical joints are the perpends. Bricks laid longwise in the wall are called stretchers, Pieces of bricks are called bats. The horizontal those crosswise headers. distance between the vertical joints (or perpends) of two successive courses is called the lap. It should equal 24 in. Figs. 245 and 246 show the Flemish bond. Its use is for appearance only. It is used in buildings and garden walls, not usually in engineering structures. The bottom of walls, spread out to comply with the conditions of the previous chapter, are called the footings. Bricks in footings must be laid as headers as much as possible; where stretchers are necessary they should be in the centre. Fig. 247 gives an example of a properly designed footing, the bottom width being twice that of the wall. The set-off on each side of each course should be 1 in. (= brick total). When such set-offs occur in any other part of the wall, on either side, forming a ledge, that ledge is called a corbel; their use is to support various parts of a structure. Regarding brick arches, fig. 248 gives a diagram in which all the technical terms are explained. Figs. 249-253 give examples of joints in brickwork. Masonry. The foregoing terms apply also to masonry. In masonry we often have stones going from back to front of the wall; they are called through stones. Their advantage is questionable; they may taper in width, but never in depth. All bed surfaces in masonry must be worked to plane surfaces. It is the duty of the engineer to see this is done. Unscrupulous masons try to make them hollow and get a better appearance on the face; this, of course, is not "engineering" at all, and a very bad practice. The joints so formed are called Flushed Joints; they are liable to splinter by the load, see fig. 254. When stones have their faces brought to a fair surface they are said to be dressed. The projecting courses often seen at the base of a wall are called plinths. When stones are sawed we have a surface left by the saw; this is called half sawing. The stones on the face of a wall or of a piece of masonry such as a bridge are brought to various kinds of ornamental facings. Of these, some examples occur in figs. 255, 256, and 257, of which perhaps the hammer-dressed has the best effect. Coming to stone walls, we have three main divisions. 1. Rubble for various purposes when the work would not be seen, such as backing retaining-walls, rough boundary-walls, pitching, and a variety of works which will from time to time be mentioned (vide Walls, Weirs, Bridges, Saddle Back Coping Roadway -Concrete ashlar Quoins Rubble Backing FIG. 258. FIG. 259. FIG. 260. etc.); it occurs as random rubble, fig. 258. Dry rubble, uncoursed rubble in mortar, random rubble built in courses, squared rubble uncoursed and coursed, figs. 259 and 260, show squared coursed rubble. Then we have ashlar. These are stones carefully worked, usually over 12 in. deep; the joints would not be more than in. It is used for facing only and quoins, fig. 259, and is in heavy work invariably backed with rubble (fig. 258) or brick work. Block in course, much used by engineers in quay walls, river walls, etc., is shown in fig. 261. It is a heavier form of squared coursed rubble. Coming to the joints used in engineering masonry, we have the joggle, fig. 262. It is used in landings to prevent movement between the stones joined, and so retain a level surface between them. The table joint appears in fig. 266. It is used in sea-wall work, and its object is to prevent lateral motion of stones, but it is very expensive, and that is why engineers now are so much in favour of casting large concrete blocks on the site for such work, with table joints or other suitable forms in them. Then we may have what is called a cement joggle. It consists of a "vee" joint on two adjacent stones. The space they form when together is run up with cement, 2 to 1 or neat. Metal cramps are much used to tie the copings of sea-walls together; fig. 265 shows one. The cramps, Block in Course which are made of thin bars of metal of a size and sectional area according to the work, are turned at the ends downwards. These ends are made rough. Mortises are then cut for them of dovetail shape and the cramp is run up with lead; they are made of iron often. It is of course liable to rust, and sometimes, though not often, bronze is used. They can, if preferable, be run up with cement to prevent the galvanic action that lead is known to set up. Sulphur and sand and asphalt have also been tried. Fig. 264 shows another way of effecting the same ends as the cramp. The mortises must be dovetailed well and the lead afterwards caulked. In fig. 267 we have another joint called the bed dowel. The dowel is made of slate. For fixing things to masonry, such as bolting engines down, etc., and railings, the rag bolt is used, shown in fig. 263. In large machinery, however, special bolts, grouted up in cement, are used. They are attached to plates at the bottom, which are firmly secured to the masonry. For lifting masonry various forms of apparatus are used. We shall consider lifting machinery in a later chapter, but a very useful device much used for the purpose of attaching blocks of stone to the crane hook is called the Lewis. It is made as shown in fig. 268. In the form shown in fig. 268 the two end pieces are inserted, then the centre one to wedge them up, and finally the ring, pin, and taper key. Fig. 269 shows a simpler form. Fig. 270 shows two ways of breaking joint in finished masonry. In no case should the headers form less than the total superficial area; is usual. Block in course with stones 7-9 in. deep is much used in spandrils, wing walls, and the faces of retaining-walls. In coursed rubble masonry the courses should be 12 in. deep if possible; the breadth of the headers should be 1 D= 18 in., and tail into the wall 3-5 times D. But the stones placed between them may be smaller, say 2 to the depth of each |