PRACTICAL DIAOKAMS. 



breadth of your circuitous border to be; stick this circumferential line full of pegs, and 

 tie one end of a garden line to one of them. Taking the other in your hand, go out to 

 the point where vou intend (he volute to begin; and as you circumambulate, holding 

 the line strained tight, you will delineate on the ground the annexed fig. 1. 



Fig. 1. Fig. 2. Fig. 3. 



A volute where the border is intended to be gradually narrowed towards the center 

 as in fig. 2, may be thus formed : — " Make a circle as before, and instead of driving 

 the pegs upright, let them form a cone ; or, instead of pegs, use a large flowerpot 

 whelmed, and, if necessary, a smaller one whelmed over it. Measure the radius of 

 your volute, and wind that complement of line round the cone in such a manner as 

 to correspond with the varying breadth of your intended border, and commence 

 making the figure at the interior by unwinding the line." 



A volute, the border of which widens as it approaches the center, is produced upon 

 the same principle as the last; only, as the figure is as it were reversed, unwind the 

 line from the other end, and fig. 3 will be produced. 



The following ingenious method of forming circles or other curvilinear lines, is the 

 invention of Mr. Forsyth, and must be of great practical use to those who have the 

 ]aying-out of grounds, particularly intricate 

 figures in geometrical gardens. Suppose a 

 b c, fig. 4, to be three points in the curve, 

 taken at equal distances 

 (say fifty links) : placing 

 the cross-stafi" at b, with 



one of the sights pointing to a, make b o perpendicular to a 

 b, and measure its length. Then, removing the cross-staff to c, 

 make c o perpendicular to b c, and equal to b o ; and make the 

 line bod equal to a o c. Then d is a point in the curve ; and in 

 the same manner other points may be found successively. 



Fig. 5 differs from the above only in this, that the angles are 

 taken outside. Set up three pegs, say fifty links apart, as before, 

 and fix the cross-staff in r, with one sight on the line r b a, and 

 the other pointing to c. Then measure r b and r c, and remove 

 to the line e c b ; draw e c equal to r b, and e d equal to r c, and 

 so on. The same end may be obtained by a theodolite, or by 

 instrument for taking angles ; or even with three needles stuck in a board, 



