40 A TREATISE OF 



There needs no centre made with boards 

 for turning thefe arches, for the earth 

 may be troflden or rammed dovvm hard 

 between pillar and pillar, and then pared 

 away elliptically. 



In plate the fecond, there are given 

 both plan and upright of a wall of this 

 kind, which makes the method more in- 

 telligible 5 and plainly fhews, that not one 

 half of the materials is funk in fuch a 

 foundation, as in one built wholly with 

 brick or ftone. 



I have lately feen fome walls built for 

 inclofing a kitchen-garden, where fome 

 part of the ground whereon the walls were 

 built, Vv^as nine or ten feet lower than the 

 furface of the defigned borders ; thefe walls 

 were carried up from the bottom of thofe 

 low places with brick- work without arches: 

 but had the method which I have propofed 

 been made ufe of, much labour and ex» 

 pence would have been faved. 



But if afhes, elms, or other forefl-trees, 

 grov/ near the outfide, it may be objefted, 

 that their roots will grow thro' thefe arches, 

 and greatly impoverifh the border -, but to 

 prevent their roots from paffing through 



a 



