CHAPTER XV. 



PRACTICAL DIAGRAMS EXPLANATORY OF THE RULES FOR LAYING OUT 

 GARDENS, MORE PARTICULARLY FOR FORMING CURVED LINES. 



To form a Volute where the border is of 

 equal breadth. — The usual mode of form- 

 ing a volute or spiral line is one of the 

 simplest problems in geometry, and 

 therefore requires no explanation here. 

 The following method is. however, both 

 original and better adapted for throwing 

 up such a figure in groundwork. It is 

 the invention of Mr Alexander Forsyth, 

 and was by him first described in " The 

 Gardeners' Magazine," from which source 

 our four following figures and descrip- 

 tions are taken. " Make a circle around 

 the centre of 

 Fig. 1012. your intended 



volute, as much 

 in circumference 

 as you intend 

 the breadth of 

 your circuitous 

 border to be ; 

 stick this cir- 

 cumferential 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 you intend the 

 volute to begin ; and as you circumam- 

 bulate, holding the line strained tight, 

 you will delineate on the ground the 

 annexed fig. 1012. 



A volute where 

 the border is in- 

 tended to be gra- 

 dually narrowed 

 towards the cen- 

 tre, as in fig. 1013, 

 may be thus for- 

 med : — " Make a 

 circle as before, 

 and instead of 

 driving the pegs 



Fig. 1013. 



upright, let them form a cone ; or, in- 

 stead 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 un- 

 winding the line." 



A volute, the border of which widens 

 it approaches 



Fig. 1014. 



as 



the centre, is pro- 

 duced upon the 

 same principle as 

 the last; only, as 

 the figure is as it 

 were reversed, un- 

 wind the line from 

 the other end, and 

 fig. 1014 will be 

 produced. 

 The 



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 laying-out of grounds, 

 particularly intricate figures in geome- 



Fig. 1015. 



following 



trical gardens. Suppose a be, fig. 1015, 

 to be three points in the curve, taken at 

 equal distances (say fifty links) : placing 



