CONSTRUCTION OF GARDEN WALLS. 



81 



bricks used — of course leaving, in the 

 former case, the opening within 10 inches 

 wide, which admits of a flow and return 

 gutter of 4 inches each. The bottom 

 and top of these tanks are formed of 

 Caithness pavement three-fourths of an 

 inch thick, and cut to exactly the outside 

 width of the wall, or Bangor slates of the 

 same breadth, half an inch thick, and of 

 as great lengths as can be conveniently 

 procured to lessen the number of joints, 

 may be substituted. These joints, in all 

 cases, should be half-checked, and put to- 

 gether with the best white lead. The 

 flow and return water may be separated 

 by having a thin slate partition set on 

 edge, and inserted into a groove cut in 

 the centre of the pavement forming the 

 floor or bottom of the tank. Three 

 courses of tanks may be used for a 

 12-feet wall, but one or two will be suffi- 

 cient for those of less heights — as the 

 smoke and heated air, passing the boiler, 

 may be conveyed either along the top 

 or bottom of the wall, so that no heat 

 from the fuel may be lost. The three 

 courses next the top are built solid, to 

 prevent the escape of heat through the 

 coping. 



The longitudinal section shows the 

 boiler a under the wall, from the top of 

 which two 4-inch cast-iron pipes rise — the 

 one to deliver the hot water to the tanks, 

 and the other to convey the cold water 

 back to the boiler again. Only one pipe 

 can be shown : the other stands imme- 

 diately behind it. Nozzles, cccc, are at- 

 tached to these pipes, each furnished 

 with a stopcock, the handle of which 

 passes through the wall, to facilitate the 

 operation of turning off or on the water 

 to any portion of the wall intended to be 

 heated. By this arrangement it will be 

 seen that the whole or any part of the 

 wall may be heated at pleasure. The 

 smoke and heated air which pass the 

 boiler, and which are in most cases com- 

 pletely lost by passing upwards through 

 the chimney, ascend as indicated by the 

 arrows, and may be made to pass along to 

 the right hand or to the left by means of 

 dampers placed in the flue at b. The 

 boiler should be placed in the middle of 

 the space to be heated, if the walls are 

 level, as by that means the water has 

 only to travel half the distance before it 

 re-enters the boiler to become heated 



VOL. I. 



again. Indeed, in regard to all modes of 

 heating walls by hot water, this arrange- 

 ment of the boiler should never be de- 

 parted from, unless in cases of difference 

 of levels, when the boiler should be placed 

 at the lowest point. 



Objections will be started to this mode 

 of heating, by some, on the plea that such 

 tanks cannot be made water-tight for any 

 length of time ; and by others, that the 

 walls must be rendered damp by evapo- 

 ration. The latter has in no case been 

 borne out by experience, as the evapora- 

 tion is confined to the depth of the tank ; 

 and if the water is withdrawn by a waste 

 pipe in autumn, at a time when it is 

 heated to its utmost extent, the heat in 

 the material will dry up the water ab- 

 sorbed, and leave the tanks as dry as any 

 other part of the wall. The only con- 

 sideration of moment to be thought of 

 is the difference of expense between such 

 a mode of heating and that of pipes, and 

 this can only be fairly estimated by local 

 circumstances. 



Dearrfs hollow brick wall. — Mr Dearn, 

 an English architect of considerable emi- 

 nence, has invented several walls, built on 

 the hollow principle, both to economise 

 material and render the walls less liable 

 to damp. The subjoined diagrams, figs. 

 56, 57, which show the elevation and 

 section of part of a wall, copied from the 



Fig. 56. Fig. 57. 



" Encyclopaedia of Cottage, Farm, and 

 Villa Architecture," will show the princi- 

 ple. " The three lower courses q, the 

 upper one of which is proposed to be 

 level with the floor, are intended as a 

 footing to the superstructure, and are laid 

 in what is called the old English manner, 

 consisting of alternate courses of headers 

 and stretchers. The next course above is 

 a stretching course on edge, p, and the 

 backing course is like it, leaving an inter- 

 val between of the width of half a brick : 

 these are then covered with a heading 

 course laid flat ; and the same system is 

 pursued until the whole height required 

 be attained." 



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