BUILDING. 



tical circular rings, or conic surfaces, 

 having the same common axis with the 

 intrados. 



Stone Walls. Stoe walls are those 

 built of stone, with or without cement in 

 the joints; the bedding joints have most 

 commonly a horizontal position in the 

 face of the work ; and this ought always 

 to be the case, when the top of a wall ter- 

 minates in a horizontal plane or line. In 

 bridge building, and in the masonry of 

 fence walls, upon inclined surfaces, the 

 bedding joints on the face sometimes fol- 

 low the direction of the top or terminat- 

 ing surface. 



The footings of stone walls ought to be 

 constructed of large stones, which, if not 

 naturally near the square from the quar- 

 ry, should be reduced by hammer dress- 

 ing to that form, and to an . equal thick- 

 ness in the same course ; for, if the beds 

 of the stones of the foundation are suffer- 

 ed to taper, the superstructure will be 

 apt to give way, by resting upon mere 

 angles or points ; or upon inclined sur- 

 faces the footings ought to be well bed- 

 ded upon each other with mortar, and all 

 the upright joints of an upper footing 

 should break joint ; that is, they should 

 fall upon the solid of the stones below, 

 and not upon tb joint. 



The following are methods practised in 

 laying the footings of a stone foundation : 

 when walls are thin, and stones can be 

 got conveniently, that their length may 

 reach across each footing from one side 

 of the wall to the other, the setting of 

 each course with whole stones in the 

 thickness of the wall should be preferred. 

 But when the walls are thicker, and bond 

 stones in part can only be conveniently 

 procured, then every other succeeding 

 stone in the course may be a whole stone 

 in the thickness of the wall ; and every 

 other interval may consist of two stones 

 in the breadth of the footing; this is plac- 

 ing the header and stretcher alternately, 

 like Flemish bond in nine-inch brickwork. 

 But when bond stones cannot be had con- 

 veniently, every alternate stone should be 

 in length two-thirds of the breadth of the 

 footing upon the same side of the wall ; 

 then upon the other side of the wall a 

 stone of one-third of the breadth of the 

 footing should be placed opposite to one 

 of two-thirds; and one of two-thirds op- 

 posite to one of one third ; so that the 

 stones may be placed in the same man- 

 ner as those of the other side. 



In broad foundations, where stones can- 

 not be procured for a length equal to two- 



VOL. III. 



thirds of the foundation, then build them 

 alternately, with the joints on the upper 

 bed of each footing, so that the joint of 

 every two stones may fall as nearly as pos- 

 sible in the middle of the length of the 

 one, or each adjoining stone ; observing 

 to dispose the stones alike on each side 

 of every footing. A wall, the superstruc- 

 ture of which is built of unhewn stone 

 laid in mortar, is called a ruble wall. They 

 are of two kinds, coursed and uncoursed. 

 The most common kind of ruble is the 

 uncoursed, of which the greater part of 

 the stones is crude, as they came out of 

 the quarry, and the rest hammer dressed. 

 This kind of walling is very inconvenient 

 for the building of bond timbers ; but if 

 they are to be preferred to plugging, the 

 backing must be levelled in every height 

 in which the bond timbers are disposed. 

 The best kind of ruble is the coursed ; the 

 courses are all of accidental thicknesses, 

 adjusted by a sizing rule, as the slating 

 of a roof; the stones are either hammer 

 dressed or axed. This kind of work is 

 favourable for the disposition of bond tim- 

 bers : but as all buildings, constructed 

 either in whole or in part of timber, are 

 liable to be burnt, strong well built walls 

 should never be bound with timber, but 

 should rather be plugged ; for if such ac- 

 cident take place, the walls will be less 

 liable to warp. 



Walls faced with squared stones, hewn 

 or rubbed, and backed with ruble stone 

 or brick, are called ashler. The medium 

 size of each ashler measures horizontally 

 in the face of the wall about 28 or 30 

 inches, in the altitude one foot, and in the 

 thickness 8 or 9 inches. The best figures 

 of stones for an ashler facing are formed 

 like truncated wedges; that is to say, they 

 are thinner at one end than at the other 

 in the thickness of the wall, so that when 

 the stones of one course, or a part of a 

 course, are shaped in this manner, and 

 alike situated to each other, 'the back of 

 the course will form an indention like the 

 teeth of a joiner's saw, but more shallow, 

 in proportion to the length of a tooth ; the 

 next course has its indentations formed 

 the same way, and the stones so selected, 

 that the upright joints break upon the 

 solid of the stones below. 



By these means, the facing and backing 

 are toothed together, and unquestionably 

 stronger than if the back of each ashler 

 had been parallel to the front surface of 

 the wall ; as the stones are mostly raised 

 in quarries of various thicknesses, in an 

 ashler facing, it would greatly contribute 



JP 



