BOOK III. 



FIXED STRUCTURES. 



807 



time, or at least when the sun shone in the beginning of summer, it might be inclined 

 to the north, (the trees being planted on the south side,) to give the trees the advantage of 

 the sun ; and during severe weather in autumn, or at any time when it was either desired 

 to protect or retard the trees, it could be inclined to the south to protect them from dews- 

 and sha'de them from the sun's rays. 



1567. The wavy or serpentine watt (fig. 241.) has two avowed objects; first, the saving of 

 bricks, as a wall in which the centres of the segments composing the line are fifteen feet 

 apart, may be safely carried fifteen feet high, and only nine inches in thickness from the 

 foundations ; and a four-inch wall may be built seven feet high on the same plan. The 

 next proposed advantage is, shelter from all winds in the direction of the wall ; but this 

 advantage seems generally denied by practical men. Miller says, he saw them tried at 

 Le Cour's in Holland, and that the trees which grew on them were in no respect supe- 

 rior to those on straight walls. They have been tried at different places in the northern 

 and southern provinces of Britain, but are generally disapproved of as creating eddies. 



1568. The angular wall (jig. 242.) is recommended on the same general principles of 

 shelter and economy as the above ; it has been tried nearly as frequently, and as generally 

 condemned on the same grounds. 



1569. The zig-zag wall (Jig. 243.) is an angular wall in which tHe angles are all right 

 angles, and the length of their external sides one brick or nine inches. This wall is built 

 on a solid foundation, one foot six inches high, and fourteen inches wide. It is then com- 

 menced in zig-zag, and may be carried up to the height of fifteen or sixteen feet of one 

 brick in thickness, and additional height may be given by adding three or four feet of 

 brick on edge. The limits to the height of this wall is exactly that of a solid wall of 

 fourteen inches thick ; that being the width of the space traversed by the angles or zig- 

 zag. That as a whole it is sufficiently strong for a fence against cattle, may be proved 

 by applying to it the first problem in dynamics ; the two diagonal lines formed by the 

 zig-zag producing an equal resistance to one line directly across a fourteen-inch wall. 

 In training on these walls, wires are stretched horizontally from angle to angle, and 

 either four and a half, or nine inches apart, or upright rods of wood (a, a] may be em- 

 ployed ; they are, however, better adapted for fences, or walls of botanic, flower, or 

 nursery gardens, than for fruit-walls. 



243 



1 570. The square fret wall (fig. 244. ) is a four-inch wall like the former, and the ground- 

 plan is formed by joining a series of half-squares, the sides of which are each of the pro- 

 per length for training one tree during two or three years. 



244 



1 571. The nurseryman's, or self-supported four-inch wall (fig. 245. ), is formed in lengths 

 of from five to eight feet, and of one brick in breadth, in alternate planes, so that the points 

 of junction form in effect piers nine by four and a half inches. This wall is the inven- 

 tion of Lee, of the Hammersmith Nursery, and is well calculated for training peaches 



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