_ ! 1. 



JOINERY. 



Joinery, have 66 ; then supposing a step to be 10 inches in 

 s -^r~~' breadth, the height should be ?=6f inches, which is 

 nearly, if not exactly, what common practice would al- 

 low. " The proportion of steps being thus regulated, 

 the next consideration is the number requisite between 

 two floors or stories : to ascertain this, we have only to 

 suppose the breadth of the steps to be given, say 10 

 inches each, as depending on the space allowed for the 

 staircase, and this, according to the rule laid down, will 

 require a rise of 7 inches nearly. Suppose then the 

 distance from floor to floor to be 13 feet 4 inches = 160 

 inches ; then J -<; J2 =:225-, which would be the number re- 

 quired. But as the steps must be equal in height, we 

 should rather take twenty three rises, provided the 

 staircase room would admit of it. 



Stairs have several varieties of structure, which de- 



Cd principally on' the situation and destination of the 

 Iding. , * 



Dog legged stairs, are those that have no opening or 

 well hole; the rail and balusters of both the progressive 

 and returning flights fall in the same vertical planes. 



Geometrical slairs, are those which have an opening 

 down the middle, and of which every step derives its 

 support from that immediately below, and from the 

 wall of the staircase. 



The steps of a stair consist of two parts, one being 

 parallel, and the other perpendicular to the horizon. 

 The part which is parallel is called the tread of the 

 step, and the other part which is perpendicular, is called 

 the riser. 



The rough timber work which is used in the support 

 of a stair, is called the carriage. 



The string board, is a board fitted against the ends 

 of the steps next to the well-hole, so as to make a com- 

 plete finish ; and the string which terminates the ends 

 of the winders, is a veneer made in the form of a spiral 

 back, with thick wood, so as to make it sufficiently 

 strong. 



The most certain method of carrying up a stair, 

 whether of stone or wood, is to provide a rod of suffi- 

 cient length to reach from one floor to the other, divid- 

 ed into as many equal parts as the risers are in number, 

 and thereby to try every step as the work advances. . 



Hand Railing. 



Hand rail- A hand rail is the upper part of the fence in a geome- 



Jng. trical stair. In order that the hand may glide easily 



along the rail without straining the body, it is evident 



that the rail ought to follow the general line of the steps, 



and to be quite smooth and free from inequalities. 



The principle of hand railing depends on the method 

 of finding the section of a right cylinder, cylindroid, 

 or prism, according to three given points in or out of 

 the surface, that is, the section made by a plane through 

 three given points in space. 



The cylinder, cylindroid, or prism, is hollow, and 

 equal in thickness to the breadth of the rail that is to 

 the horizontal dimension of its section, and the ends or 

 bases, the same as the plane or projection upon the 

 floor. 



The hand rail of a stair may always be formed of a 

 portion of this cylinder, cylindroid, or prism, the base 

 of which is the plane of the stair ; for the hand rail it- 

 self must stand over the plane, it will therefore be con- 

 tained between the vertical surface of the cylinder, cy- 

 lindroid, or prism. And as the hand rail is got out in 

 portions, so that each portion may stand over a quadrant 

 of the circle, or ellipse, which forms the plane, we 

 may also suppose such a portion contained between two 



parallel planes, so that the portion of the hand rail may Jointly. 



be thus contained between the two cylindrical, or cylin- *> y"'' 



droidic surfaces, and the twT> parallel planesr The parts 



which are to be joined together to for?h the rail, are to 



be prepared in such a manner, that when set upon 



their place, all the sections which may be supposed to 



be made by a vertical plane passing through the axis of 



the cylinder, or cylindroid, may be rectangles, and this 



is called the squaring of the rail ; which is all that can 



be done by geometrical rules. 



Now, as hand rails are not made of such portions of 

 hollow cylinders or cylindroids, but of plank wood, we 

 have only to consider how such portions may be form- 

 ed from a plank sufficiently thick. As the. faces of the 

 plank are planes, we may suppose the rail contained be- 

 tween two parallel planes, that is, between the two faces 

 of the plank. Then such figures are to be drawn on the 

 sides of the plank, that, when the superfluous parts are 

 cut away, the surfaces that are formed between the op- 

 posite figures are portions of the external and internal 

 cylindrical or cylindroidic surfaces. A mould made in 

 the form of these figures, is called thejace vi'mld, which 

 is only a section of the cylinder or cylindroid through 

 three points in space. 



The vertical, or cylindrical, or cylindroidic surfaces 

 being formed, the upper and lower surfaces must next be 

 formed. This is done, by bending another mould round 

 one of the cylindrical or cylindroidic surfaces, generally 

 made to the convex side, and drawing lines oh the sur- 

 face round the edges of this mould. Then the super- 

 fluous wood is cut away from the top and bottom, so 

 that if the piece were set in its place, and a straight 

 edge applied upon the surfaces now formed, and direct- 

 ed to the axis of the well hole parallel to the horizon, 

 it would coincide with the surface. The mould thus 

 applied upon the convex side to form the top and bot- 

 tom of the piece, is called the falling mould. 



To find these moulds, the plan of the steps and rail 

 must first be laid down ; then the falling mould, which 

 must be regulated by the heights of the steps ; and 

 lastly the face mould is ascertained by the falling mould, 

 which furnishes the three heights alluded to. 



PlateCCCXXXVIII.Fig. 1. Is a dog-legged staircase. PLATE 

 No. 1. is the plan. No. 2. the elevation, shewing the ccczxxvm. 

 rough strings under the steps, and the sling rod marked '"'S- ! 

 into equal divisions, for regulating the work in the pro- 

 cess of putting it up. The dotted lines above the rail, 

 drawn by the square, show how the centres of the arcs 

 that form the ramp are found. 



Fig. 2. Geometrical staircase with winders. No. 1. Fig. 2. 

 is the plan. No. 2. the elevation and section. As the 

 staircase is supposed to be cut through the middle, pa- 

 rallel to its length or longest dimension, it would be ab- 

 surd to represent the whole elevation, as is frequently 

 done ; for this reason, only the farther, half is represent- 

 ed, and the steps of the other half are shewn by dotted 

 lines. 



Fig. 3. Geometrical staircase without winders. No. Fig. 3. 

 1 . is the plan. No. 2. the elevation. It is in such con- 

 structions as this and the last figure, where great nicety 

 of workmanship, and skill in geometrical lines, are found 

 necessary. 



Fig. 4-. A section of the rail and mitre cap for a Fig. 4. 

 dog-legged staircase. The dotted lines are drawn from 

 the section of the rail. No. 1. to the mitre. No. 2. in 

 straight lines. From thence in the arcs of circles, to 

 the straight line passing through the centre of the cap 

 at right angles to the former straight lines, then perpen- 

 diculars are drawn, and made equal in length to the 



