Garden and Asricidtural Structures. 



195 



48 



ill 



iJJi 



of a hammer would only punch a hole through, without shat- 

 tering the slate. In Wales and Cumberland, slates ; in the 

 iron districts, and in London, bricks,* in Yorkshire, Lan- 

 cashire, and Scotland, sandstone flags ; and, in America, timber, 

 would be the cheapest filling materials. 



Slate walls made in the way last mentioned, with the addi- 

 tion of eyes cast to one side of the iron uprights for the wires 

 of a trellis, and the slates painted black, would appear to be 

 the best garden walls that could be erected. 



They could harbour no insects, would not 

 be eaten out by nailing, would look better than 

 brick walls, and the tops of the uprights be 

 available for rolling-blinds, &c., for protec- 

 tion. 



Perhaps the deep violet colour of the slates 

 would be the best possible for garden walls, 

 which I deduce from some I'ecent observations 

 on the rays of light and heat. 



These slate walls might be hollow, viz. filled 

 with rounded pebbles and nothing else, and 

 thus be heated by steam occasionally, or be 

 entirely hollow, with a double rabbet, and per- 

 forated uprightly, and become long smoke flues 

 of great depth and thinness, as in^. 48., in 

 which d is the side view of an upright, and 

 e a cross section or plan. 



There is no difficulty in procuring slates with 

 square-sawn edges, 4 ft. square or more ; and, 

 if the trees were tied with twine, or spun yarn 

 boiled in Indian-rubber varnish, ar even in oil, 

 a great saving in nails, shreds, labour, and 

 repairs of walls would accrue. 



Walls with a southern aspect might have 

 the back side, viz. the north aspect, painted 

 white, or covered with straw matting ; or ivy 

 might be permitted to grow on them, to pre- 

 vent the radiation of heat on that side. The roots of trees 



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