CONSTRUCTION OF GARDEN WALLS. 



83 



height, two catches, a a, at each end, will 

 fly out by means of weight at their tails, 

 as shown at a ; and these will hold the 

 gauge-box in its proper station till it may 

 require again to be raised." It will readily 

 be seen that, by the use of this box, the 

 vacuities will be perpendicular ; whereas, 

 by using planks in the way described 

 above, they will be horizontal, and calcu- 

 lated for the circulation of heat by either 

 of the means proposed, which the perpen- 

 dicular vacuities would not admit of. 

 The great advantage of hollow stonewalls 

 is to resist damp, and hence they are 

 well adapted for dwelling-houses. 



Stone walls, built sufficiently thick to 

 admit of the interior being filled up with 

 loose stones without mortar, are warmer 

 than solid ones of the usual size, parti- 

 cularly in the case of walls having a 

 southern aspect ; because the heated air 

 from the sun, passing through the south 

 side, is retained amongst the loose stones, 

 and prevented from passing through the 

 north or cold side by conduction — the cold 

 side having a tendency to abstract the heat 

 from the south or warmer side. Hence all 

 south walls, of whatever material, should 

 be of greater thickness than those facing 

 the east or west, if it is wished that the 

 greatest amount of heat should act on the 

 south side ; because, from the much greater 

 cold on the north side, it is continually 

 abstracting heat from the warmer side 

 opposite to it. Walls with east and west 

 exposures are more uniform in tempera- 

 ture on both sides, as they are not subject 

 to the same rule — they receive heat 

 equally, and part with it equally. 



SilverlocF s hollow brick wall. — This wall 

 is the invention of Mr Silverlock, a re- 

 spectable nurseryman at Chichester, and 

 has been extensively used both for gar- 

 den walls and dwelling-houses. " It is 

 constructed of bricks set on edge, each 

 course or layer consisting of an alternate 

 series of two bricks placed edgeways, and 

 one laid across, forming a thickness of 

 9 inches, and a series of cells, each cell 9 

 inches in the lengthway of the wall, 4 

 inches broad, and 4^ inches deep. The 

 second course being laid in the same 

 way, but the position of the bricks alter- 

 nating, or breaking joint with the first, the 

 result will evidently be a hollow wall, 

 with communicating vacuities of the 

 above stated dimensions, equally distri- 



buted from the bottom to the top of the 

 wall. Fig. 64 shows the elevation of such 

 a wall, which differs only from the hollow 



Fig. 64. 



1 1 II 





ii 'II ' 



±= 





ii ii 





1 1 





II II 



1 1 





wall of Dearn in being carried up in 

 Flemish instead of English bond. Fig. 

 65 shows the manner in which piers may 



Fig. 65. 



be built in such walls, so as to project 

 equally on both sides, for application to 

 the east and west walls of gardens, both 

 sides of which are equally valuable for 

 training fruit trees; and fig. 66, how a 



Fig. 66. 



pier may be built on one side only, for 

 application to the north and south walls, 

 the south sides of which are chiefly 

 valuable for fruit trees. The saving in 

 this wall is one brick in three, but the 

 bricks and mortar must be of the best 

 quality. One great advantage of these 

 walls is, that they admit of being equally 

 heated throughout, by a tube of hot water 

 conducted along the interior, just above 

 the surface of the ground. It is evi- 

 dent that brick walls on the same plan 

 might be built of 18 inches or 2 feet in 

 width, or indeed of any width, by joining 

 two 9-inch hollow walls together, as in 

 fig. 67, which, if a garden wall, might be 



Fig. 67. 





















































— 







































heated on one side, without being heated 

 on the other, by carrying up the heading 



