BOOK IV. 



ARRANGEMENT OF QUANTITIES. 



377 



367 



practical geometry, that the same object may be attained by an adjusted triangle (such as 

 e\ the extremities of which will indicate points in the circumference without further 

 trouble. 



1 930. Other modes on similar jrrinciples, well known to 

 land-surveyors, are occasionally resorted to in laying out 

 gardens, especially in the geometric style, and in preparing 

 the foundations of farmeries, and other rural offices and 

 appendages. A very obvious application of it is that of 

 reducing an irregular basin of water to a circular figure. 

 The director moves round with the adjusted triangle 

 (Jig. 367. a) ; his assistant sets off the dimensions and as each 

 point in (he circumference is ascertained, it is marked by a 

 stake (b, c, rf). 



1931. A level line (Jig. 368./,/), whether straight or 

 curved in direction, can only be determined on an irregu- 

 lar surface by measuring down from an elevated level line (a), or from level lines in 

 parallel directions, and so transferring the points by horizontal levels to the proper line. 

 Straight rods are the ready means of measuring down, and the points must be marked 

 by hillocks or hollows (6) ; or by smooth-headed stakes driven into the surface, and pro- 

 truding above, or sunk under it, according to the obstructions. 



368 



1932. Lines of uniform acclivity or declivity (Jig. 368. e, e, e] are readily formed on 

 the same principle. In this and the former case, the common level and the borning- 

 pieces (a and rf), with measuring rods and stakes, are all the instruments required. The 

 formation of level lines and uniform slopes, by the borning-pieces and common level, 

 ought to be familiar to every working-gardener ; for, without considerable adroitness in 

 this department of garden-operations, none can be considered as fit to form a walk, or 

 even plant a box-edging. 



1933. Levelling for terrace-slopes (Jig. 369. )> or for geometrical surfaces, however 

 varied, is performed by the union of both modes, and requires no explanation to those 

 who have acquired the rudiments of geometry, or understand what has been described. 



369 



SUESECT. 3. Of tJie Arrangement of Quantities. 



1934. The dividing and subdividing of land is generally the business of the land-sur- 

 veyor, but it sometimes comes under the practice of the gardener, on a small scale, and on 

 simple principles. Thus it may be required to determine the dimensions of a square, of a 

 circle, of an oval, or of a mixed figure of a kitchen-garden, which shall contain a certain 



