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Shaft

column, diameter, line, bottom, drawing, height, equal, draw and leg

SHAFT, (from the Saxon seeaft,) that part of a column which, in the classic examples, may be denominated the fits tram of a conoid, situate between the base and capital; it is also called the fast, trunk, or body of the column.

By some architects, columns are diminished from one-third upwards ; this occasions a very gouty appearance. Some architects and builders, however, have fallen into the con trary error, by making the sides of columns in a straight line from the base to the capital. Mr. Revely, in his Prefitee to the third volume of Stewart's Athens, expressly says, that all the columns he had seen in Greece were diminished with a gentle curve. The curve is so gentle, that the straight line, which is a tangent at the bottom of the shaft, is not parallel to the axis, but falls nearer to it at the top of the column than at the bottom. For the method of diminishing the shaft of a column, see COLUMN.

The method of drawing the shafts of columns upon paper in the most expeditious manner, will be a very useful addi tion to this article.

Figure 1.—To represent a fluted column, the height of the column, its diameter at the bottom, and the ratio of the two diameters, being given.

Let A II represent the height and axis of the pro duce A U to c, make A II c to BC in the ratio Of the diameter at the base, to its diameter at the capital ; draw a line through A, and another through a, at right angles to A ; set half the diameter of the column from A on each side of it, and divide the whole length of this line into parts repre senting the ratio of the flutes orthographically projected; from the points of division draw lines to c, to meet the line passing through n, and the lines thus drawn will represent the shalt of a column as fluted.

In this example An-l-nc is to a c as 4 to 3, therefore the point c will be found by repeating A n four times from A to e.

Figures 1, 2., 3, 4, represent a range of columns, three of which are here supposed to be drawn by this or the (01 lowing means, which will be made sufficiently plain by reference to the plate :— Suppose a compass joint-rule, as in Figure 4, bevelled on the upper sides of the inner edges; from a, the centre of the joint, set on the inner edge R r as many times the height of the shaft, P e, as the diameter at the bottom contains the difference of the two diameters; lay the edge of the rule upon the axis, with the point P on the middle of the bottom diameter, s u; draw the other leg of the rule out to any convenient distance, while the marked leg is kept fast upon the axis ; then pressing down the leg which is not over the work, move the marked leg to any point in s u, and draw a line by it, which will represent a flute ; and all the other flutes may be drawn by repeating the operation. If the two lines which terminate the breadth of the column be con tinued downwards to D and o (Figure 1) at the waste edge of the paper, and also the axal line A n, the fluting may be projected by means of the semicircle n n t o; the line o 0 being supposed at right angles to A B. On D o describe a

semicircle, and draw the tangent line a F parallel to D 0, cutting c D and c o at E and F; then from a and F draw lines to the centre, cutting the circumference at ii and i; divide the arc it I into five equal parts, set two on the arc n n, and two on the arc r o, which will be the points for the angles on the semi-circumference ; and from these points draw lines to c between the diameters at A and B.

Figures 1, 2, 3, 4, are four equal shafts of columns, placed at equal distances, and supposed to constitute a part of the drawing of a Doric portico. The method of drawing the flutes to a point is most expeditiously performed by means of a joint-rule in the following manner :—Whatever be the intended height of the drawing of the shafts, set as many times that height from the centre of the joint on the inner edge of the rule, as the diameter of the column at the bottom contains the excess of that diameter above the tipper diameters. Let us suppose that the upper diameter is to the lower as 3 to 4, as in the plate, then P Q being the representation of the height of the shaft, make R P on the edge of the rule equal to four times P Q; and lay the edge R P on the line represent• ing the axis of the column ; while a P is in this position, move the other leg out to any distance, and press upon it so as to make it stationary ; then revolve the leg that was first sta tionary, and the point R will still keep its situation in the axis of the column, so that the moveable leg of the rule, moving round the centre of the joint, will answer the same purpose as a straight-edge moving round a pin ; but it is much handier, for if the point falls on the paper, we shall have no occasion to prick it; and if the point extends beyond the surface. of the board, we can still use the joint-rule with as much correctness as if the point were in the drawing board. Figures 5 and 6 exhibit a very correct modification of the principle just explained. Find the point v as above, extend the axal line v w to the bottom of the board at where the paper is intended to be cut off when the drawing is finished ; then if the upper diameter is to be one-sixth less than the lower diameter, divide a b, Figure 6, of the same length into six equal parts, and if the column be eight diameters in height, divide the lower sixth part into eight equal parts ; then on the point it describe the semicircle c, k, d; with a radius equal to one of these parts, circumscribe the rectangle c, f, e, d, and divide the flutes as before.

Figure 7 is the method of drawing the flutes by dividing both diameters in the same ratio as shown by the plan at the bottom.