196 



Economical Mode of building 



planted against such walls would have less interruption than 

 against brick walls built in the common or even the best way, 

 viz. upon piers. 



The joints of the slates might be put together with tar, 

 which would prevent insects from ever touching them, and 

 make them steam or smoke staunch. 



On the top they should have a cast-iron coping, locking 

 into the top of the uprights, which might either be let into 

 blocks of stone at the bottom, or cast with a broad base to 

 bury in the earth. The bottom row of slates should rest 

 upon a range of bricks, or be let into a cast-iron bar, i. e. an 

 upright laid flat, and not perforated, into which they could be 

 rabbeted. Where sheds or houses of any kind were erected 

 with these walls, the uprights might be fastened to the blocks 

 of stone by three eyes cast in a bottom flanch, or in three 

 lugs (ears), through each of which a large nail should be 

 driven into a plug of hard wood driven into a jumper hole 

 in the block of stone, as in^. 49., in which a is the section, 

 and b the plan. Two lugs, c c in Jig, 50., would in general 



50 



r^ 



O 



be all that would be necessary, as controlling the motion of 

 the post in the only direction possible, viz. perpendicular to 

 the plane of the wall. This is the way in which railway chains 

 are fastened down, and it is an exceedingly effective and cheap 

 mode. 



Two striking applications of such walls as these occur to 

 me : first, that houses so built, having walls only one third 

 the usual thickness, will have the advantage of larger apart- 

 ments on a given ground plan, than those built in the ordinary 

 way ; an advantage not slight when ground is dear, as in large 

 cities : and, secondly, that, by means of these cast-iron ties 

 and uprights, walls of any magnitude may be built of such 

 rigidity, that when built upon a bad foundation, even upon 

 soft mud, they will subside en masse, and without shakes 

 or cracks. For this purpose it is only necessary to divide the 



