N

2186. In fig. 783. X is the plan and Y the elevation, or rather section, of a geometrical staircase. AB in X is what is called the cur-tail step (curved like the tail of a cur dog), which must be the first step fixed. CCC are the flyers supported from below by rough carriages, and partly from the string board DHEF in Y. The ends next the wall are sometimes housed into a notch board, and the steps then are made of thick wood and no carriages used. GGG are winders fixed to bearers and pitching pieces, when carriages are used to support the flyers. The winders are sometimes made of strong stuff firmly

wedged into the wall,
the steps screwed to-
gether, and the other
ends of the steps fixed
to the string DEHF.
In all cases of wooden
geometrical stairs their
strength may be greatly
augmented by a flat bar
of wrought iron coin-
ciding with the under
side and screwed to the
string immediately be-
low the steps. HIK

in Y is the wall line of

CCC

Fig. 783.

B

X

Where the space

the sofite of the winding part of the stairs, and LMN part of the rail supported by two balusters upon every step. of the going of the stairs is confined, the French have long since introduced, as in fig. 784., the practice of placing the balusters outside the steps, which affords more room for persons ascending and descending.

Fig. 784.

HANDRAILS AND CUR-TAIL STEP.

2187. The upper part of the fence formed by capping the balusters of stairs is called the handrail, whose use, as its name imports, is for a support to the hand in the ascent and descent of stairs. The hand, for support to the body, should glide easily over it without any strain, whence it is evident, that to be properly formed, it must necessarily follow the general line of the steps, and be quite smooth and free from inequalities. It must be obvious to the reader who has thus far followed us throughout the different previous portions of our labours, that the chief principle of handrailing will be dependent on the methods of finding sections of cylinders, cylindroids, or prisms, according to three given points in or out of the surface, or, in other words, the section made by a plane through three given points in space. The cylinder, cylindroid, and prism are hollow, and of the same thickness as the breadth of the rail, or the horizontal dimension of its section; and their bases, their planes or projections on the floor. Thus is formed the handrail of a staircase of a portion of a cylinder, cylindroid, or prism whose base is the plane of the stair, for over this the handrail must stand, and is therefore contained between the vertical surface of the cylinder, cylindroid, or prism. As the handrail is prepared in portions each whereof stands over a quadrant of the circle, ellipse, or prism of the base which forms the plane, such a portion may be supposed to be contained between two parallel planes, so that the portion of the handrail may be thus supposed to be contained between the cylindrical, cylindroidal, or prismatic surfaces and the two parallel planes. The parts to be joined together for forming the rail must be so prepared that in their place all the sections made by a vertical plane passing through the imaginary solid may be rectangular: this is denominated squaring the rail, and is all that can be done by geometrical rules. But handrails not being usually made of these portions of hollow cylinders or cylindroids, but of plank or thicknesses of wood, our attention is naturally drawn to the consideration of the mode in which portions of them may be formed from planks of sufficient thickness. The faces of the planks being planes, they may be supposed to be contained between two parallel planes, that is, the two faces of the plank. Such figures, therefore, are to be drawn on the sides of the plank as to leave the surfaces formed between the opposite figures, portions of the cylindrical, cylindroidal, or other surfaces required, when the superfluous parts are cut away. A mould made in the form of these figures, which is no more than a section of them, is called the face mould. 2188. The vertical, cylindrical, or cylindroidal surfaces being adjusted, the upper and lower surfaces must be next formed; and this is accomplished by bending another mould

round the cylindrical or cylindroidal surfaces, generally to the convex side, and drawing lines on the surface round the edge of such mould. The superfluous wood is then cut away from top to bottom, so that if the piece were set in its place, and a straight edge applied on the surfaces so formed, and parallel to the horizon directed to the axis of the wellhole, it would coincide with the surface. The mould so applied on the convex side for forming the top and bottom of the piece, is called the falling mould. For the purpose of finding these moulds it is necessary to lay down the plan of the steps and rail; next, the falling mould, which is regulated by the heights of the steps; and lastly, the face mould, which is regulated by the falling mould, and furnishes the three heights alluded to.

2189. Fig. 785. ex

hibits two of the most usual forms of handrails. A is that most commonly employed, that marked B is called a toad's back rail.

2190. Fig.786. shows the method of drawing the scroll for terminating the handrail at the bottom of a geometrical staircase. Let AB be the given breadth ; draw AE perpendicular to AB, which divide into eleven equal parts, and make AE equal to one of them. Join BE, bisect AB in C and BE in F. Make CD equal to CF and draw DG perpendicular to AB. From F, with the radius FE or

FB, describe an are

cutting DG at G. Draw GH perpendicular to BE cutting BE at O. Draw the diagonals DOK and IOL perpendicular to DOK. Draw IK parallel to BA; KL parallel to ID, and so on to meet the diagonals. From D as a centre, with the distance DB, describe the are BG. From I as a centre, with the distance IG, describe the arc GE. From K as a centre, with the distance KE, describe the arc EH. From L as a centre, with the distance LH, describe the arc HP. Proceed in the same manner and complete the remaining three quarters, which will finish the outside of the scroll. Make BR equal to the breadth of the rail; namely, about two inches and a quarter. Then with the centre D and distance DR describe the arc RS, with the centre I and distance IS describe the arc ST, and with the centre T and distance KT describe the arc TU, and the scroll will be completed.

2191. Fig. 787. gives the construction of the cur-tail step, or that which lies under the scroll, abcd is the veneer that covers the riser; efgh, the nosing of the cover or horizontal part of the step; ikl the face of the string board, and mno the projection of the nosing.

2192. In fig. 788. is shown the cover board for the cur-tail step, abcd and efgh in dotted lines represent the plan of the scroll; opqrs, the nosing of the curtail step; t, u, v, s, the nosings and ends of the risers. The circle 1, 2, 3, &c. is described from the centre of the scroll, and divided into equal parts equal to the distances of the balusters from centre to centre, and lines are drawn to the centre of the scroll in order to ascertain the middle of the balusters, by giving a regular gradation to the spaces. The whole of the spiral lines in this and the previous figure are drawn from the same centres as the scroll.

FORMATION OF BODIES BY JOINING THEM WITH GLUE.

2193. The way in which bodies are glued up together for different purposes will be given below, and with them will close this section.

2194. Fig. 789. shows at A a section of two boards glued up edge to edge. At B the face of the same is seen. C shows the section of two boards glued edge to edge, each piece being grooved, and a tongue inserted at their junction. By similar means a board may be increased to any width, be the pieces whereof it is composed ever so narrow. D shows two boards fixed at right angles, the edge of one being glued on the side of the other. A block for the purpose of strengthening the joint is fitted and glued to the interior side.

Fig. 790.

2195. Fig. 790. A is a section of two boards to be joined at an oblique angle. They are mitred and glued together with a block at the angle. B shows the inner sides of the boards so fixed. It is by repeating this operation that columns are glued up.

2196. Fig. 791. A is the section of an architrave. The moulding is usually, if not always, glued to the board; the vertical line therefore, showing the extreme boundary of the moulded part, is the sec

Fig. 791.

C

D

E

faces to be glued together in contact, till after they are set and fully held together, being knocked off when the glue has become hard, and then the moulding shown at A and B is stuck.

Fig. 793.

Fig. 794.

courses, where the vertical joints are made to break, as seen in the elevation A. 2198. In fig. 793. is exhibited the mode in which veneers are glued together for the purpose of forming cylindrical surfaces. Brackets with their faces upwards are nailed to

a board. Their ends are perpendicular, and a cavity is left between them sufficient to receive the veneers and wedges. In A the thin part in the form of an arc shows the veneers as in the state of glueing, the wedges being on the convex side. B is a section of the board and bracket. The work when putting together should be dry and warm, and the glue should be hot. When this last has set hard, the wedges must be slackened, and the veneers, which now form a solid, taken out.

2199. Fig. 794. is a strong method of forming a concave surface by laying the veneer upon a cylinder, and backing it with blocks in the form of bricks, which are glued to the convex side of the veneers and to each other. The fibres of the blocks are to be as nearly as possible parallel to the fibres of the veneers. A is the section of the cylinder veneer and blocks, and B shows the convex side of the blocks.

2200. Fig. 795. is another mode of glueing veneers together with cross pieces screwed to a cylinder, the veneers being placed between the former and the latter.

2201. In fig. 796. is shown the method of glueing up columns in pieces, which here are The workeight in number, each being glued to the other after the manner of fig. 790. man should be careful to keep the joints out of the flutes, when the columns are to be A is fluted, by which the substance will be more likely to prevent the joints giving way. a section of the column at top, and B at the bottom. After glueing together, the octagons In B are and mitres should be correctly laid down for the true formation of the joints. shown two bevels, one

for trying the mitres, and the other for trying the work when put together.

2202. Fig. 797. is the mode of glueing up the base of a column. It is formed in three courses, the pieces in each of which are made to break joint over one another. The horizontal joints of the Courses must be so adjusted as to fall at the junction of two mouldings, forming a

Fig. 798.

re-entering angle. After the glue is set quite hard, the rough base is sent to the turner, by whom it is reduced into the required profile. The fibres of the wood should lie horizontally, in which direction the work

Fig. 799

will stand much better than when they are vertical. A is the plan of the base inverted, and B is the elevation.

2203. The formation of a modern Ionic capital is given in fig. 798., wherein A is the plan inverted, showing the method of placing the blocks; and B is the elevation.

2204. Fig. 799. is the method of glueing up for the leaves of the Corinthian capital, A is the plan inverted, and B is the elevation. The abacus is glued up in the same manner

as in the preceding example.

2205. Fig. 800. exhibits the mode of forming a cylindrical surface without veneers, by means of equidistant parallel grooves, A is the elevation, and B the plan.

2206. Fig. 801. exhibits the method of covering a conic body. It is, in fact, no more than covering the frustum of a cone, and is accomplished by two concentric arcs terminated at the ends by the radii. The radius of the one arc

is the whole slant side of the cone, that of the other

In this case,
and filled in
The plan is

is the slant side of the part cut off.
the grooves are directed to the centre,
with slips of wood glued as before.
shown by the circle ABC. The arc HI must be
equal to the circumference ABC.

2207. Fig. 802. shows the same thing for a smaller segment.

2208. Fig. 803. shows the manner of glueing up a globe or sphere by the same method. A is the face of the piece; B the edge showing the depth of the grooves; C shows the mould for forming the piece to the true curvature; and D the faces of two pieces put together.

C

D

Fig. 803.

SECT. VI.

SLATING.

2209. An account of the materials used by the slater have been detailed in Chap. II. Sect. VIII., and will not leave us much to say on their application.

2210. The tools used by this artificer are the scantle, which is a guage by which slates are regulated to their proper length; the trowel; the hammer; the zaz, an instrument for cutting the slates; a small handpick, and a hod and board for mortar.

2211. Slating is laid in inclined courses, beginning from the eaves and working upwards, the courses nearest the ridge of the roof being less in width than those below. The lap of one slate over another is called its bond, and it is the distance between the nail of the under slate and the lower end of the upper slate. The bed of a slate is its under side, and the upper side is called its back. The part of each course which is exposed to the weather is called its margin. The slates are nailed to close or open boarding lying on the back of the rafters with nails, which should be of copper or zinc. If iron nails are used they should be well painted. The operation of cutting or paring the side and bottom edges of the