Thickness:, Cement and Materials of JValls> 205 



cape its penetration. It brings along with it, the ingre- 

 dients of which it is usually composed ; and cr}-stalli- 

 zation is perfected in the interior lime, though more 

 time be occupied in the process. But before all, the 

 stone, in size and texture, being proportionately large 

 and sound, constitutes the principal strength of any ma- 

 sonry, well and faithfully put together. Therefore a 

 thinner wall of sound and large stone, is far preferable 

 to one composed of small stone ; however in thickness 

 it may exceed. Loriot''s theory of w^alls, has already 

 become obsolete. Time indeed gives opportunity, in 

 any walls, for the lime to recover its jixahle air ; and 

 again to petrify. But in those whereon pressure is im- 

 mediate, and strength at once required, time cannot 

 be afforded. 



* Pise walls^ composed entirely of common earth, 

 plumb, and well packed, rammed and consolidated, are 

 stronger and better, for ordinary purposes, than those 

 of stone, indifferently built, and composed of inefficient 

 materials. For some uses, they ai'e as good as stone 

 walls. It would be well to select, and publish for in- 

 formation, a concise account of this cheap and excel- 

 lent mode of erecting walls. For most farm buildings 

 they would be perfectly competent. — See Johnson'' s Ru- 

 ral (Economy^ for an account of Pise walls. 



The great mistake made by rough casters, is that of 

 using mortar over rich. I have experienced the folly 

 of this practice ; and know the advantages of its oppo- 

 site. Where gravel, from which all other matter has 

 been screened ; and where that and small pebbles are 

 dashed in; the mortal- will bear more lime. Because 

 the gravel and pebbles afford surfaces, around which 

 the extra quantity of lime crj^stallizes. In the common 



