This section is from the book "The Gardener V2", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
At the commencement of these papers I pointed out that in drawing any geometrical figure, or group of figures in a geometrical design, it was first necessary to have two or more lines crossing each other at right angles at the centre of the figure or group, to keep all the parts exactly on the square. The same number of lines that are found necessary to draw the design on paper is required for the same purpose when laying it out on the ground. If a flower-garden has to be laid out on a piece of ground which has been levelled and is about to be turfed over, these lines may be marked out by laying a line and taking out shallow drills, such as are taken out for small seeds. The lines may be made perpendicular by the same rule given for drawing them on paper, using either of the compasses described in this chapter. It is, however, desirable to have a large T square for this purpose. This may be made by any joiner. The legs should be 8 or 10 feet long. The various centres, etc, can be measured from these perpendicular lines, pegs inserted to mark them, and the whole design traced out on the level surface. A number of pegs should then be inserted all round the flower-beds, but at a distance of 2 inches inside of where the turf will ultimately be cut, to permit of a good edge being got.
When you have pegged out each bed, with a peg at each centre, the perpendicular lines are of no further use. The ground may then be lightly pointed over where the turf has to be laid, and the work proceeded with as before described. When a design has to be laid out on a lawn, lines will have to be stretched to serve as perpendicular lines, till the centres, etc, are accurately marked by inserting pegs. To facilitate the laying out of flower-gardens, and also in preparing flower-beds for planting, especially carpet-beds, a ground-compass is of very great service. A very good ground-compass may be made by any ordinary joiner. It may be made from 3 to 5 feet long, the wood being good, sound, well-seasoned Ash, 4 inches wide and 2 thick. The joint at the top, and the legs, may be formed similar to an ordinary drawing-compass; but instead of making both legs with sharp points, make one stouter at the end, and have it fitted into the top of a short stout peg, such as is shown at a, fig. 59, so as to form a joint, with a wood peg through it, the same as at the top.
This is of much importance when working on soft ground, as the other leg can be extended to its utmost extent, while the peg a still stands firm and upright in the centre of the circle, keeping the circumference quite true, which would be more difficult to do were both legs alike. A compass of this sort should also be fitted with a semicircular piece of stout sheet-iron, fixed into one leg and passed through an opening in the other, as shown, with a thumb-screw to fix it at any desired radius. The other leg of the compass should be reduced to a point, and shod with iron to keep it from wearing or getting broken. The beam-compass is an article which any gardener, with a little assistance from a blacksmith, may make for himself. Get two iron rods, 2 feet long and 1/2 inch thick - similar to those shown at a b, fig. 60 - pierced with small holes 3 inches apart. The rod a should have a thickish shoulder worked upon it, some 6 or 8 inches from its point, for the double purpose of steadying it in the ground and supporting the lath or beam part of the compass. Rod b should be made with a sharp point for tracing out figures on the ground. The lath should be 10 or 12 feet long, 2 inches wide, and 1 inch thick.
Mark this off into feet and inches after the manner of a garden measuring-rod, and get it pierced with holes the same size as the iron rods at every inch of its length, so that rod a may be shifted to any desired point. These holes will not have to be made in one row along the centre of the lath, but in two or three rows, zigzag fashion, as there will be less chance of the lath splitting in two. By placing a short piece of stout wire through the hole nearest to the point of rod b, after passing it through the lath, it will prevent the latter from slipping off while the circle is being described by swinging it round by the handle of the rod. A similar piece of wire placed through either of the holes in rod a will serve to support the lath farther from the ground, should anything intervene between the centre of the circle and the circumference to make that necessary. It will of course be understood that in marking off the feet and inches on the lath, the measurement must start from the first hole, or that through which the rod a is to be placed.
Both these forms of compasses have a fault - their radii are limited. The simplest of all compasses for ground work, and which has not this fault, is represented at fig. 61. This is simply a peg inserted at the centre of the circle, the looped end of a line placed over it; the line is then put twice round a peg at the circumference, as shown in our fig., the loose end of the line being grasped and held tight by the left hand, while the peg b is held in the right. By this means a circle can be drawn quite as accurately as with a compass, and of any dimensions - it being only a question of length of line. If the line is placed properly round the peg b, as is shown, the latter has only to be turned round to the right or left to increase or diminish the radius; and on this account, when once set to the proper radius, the peg has to be held very steady while tracing out the figure.
Just a few words more about cutting turf edges. In setting pegs round curved beds or edges of walks, for this purpose you must consider which side of the peg your line will occupy. At a a, fig. 62, the line is between the pegs and the walk - or, in other words, your edge is on the outside of the circle. In this case the edging-knife should come close up to each peg, giving it, as near as the eye can guess, the proper sweep between the pegs. On the other hand, when the line is behind the pegs, your edge being inside the circle, as seen at b b, the pegs must be placed a little farther back, so that when cutting the edging the knife will come up to the line half-way between the pegs, giving it the proper curve between these points, which will have the pegs more or less inside the edge. It is sometimes more difficult to cut a straight edge well than to cut round a curve. In doing this many make the mistake of cutting close to the line, and very often displace the line. In the first place, the line should be made very tight; and after making sure that all is right, place your right foot on the line about a yard from the end, and with the edging-knife make a clean, straight cut, about half an inch from the line up to where your foot is on the line and then, before lifting your foot, place the edging-knife across the line to keep it in its place, while you move your foot back another yard upon the line.
This process is quite necessary when there are any irregularities in the edging, if a straight edge is wanted; and it is safe to adopt it even when the edge is quite smooth. R. Inglis.