Thickness y Cejnent and Materials of Walk, 201 



cannot enter the stone, it is called, vulgarly and impro- 

 perly, sweating; though it is occasioned by the texture 

 being impervious, and not permitting the damp to en- 

 ter. Faults and cellars^ to be dry, should be built with 

 soft, and clean gritted stone. Hard stone aie thought 

 best, to withstand attempts at breaches in jails; and for 

 forts, and other works requiring strength; or subject to 

 forcible assaults. However true this may be to a cer- 

 tain point, the idea is generally extended too far. A 

 soft, tough, curly stone, will not break nearly as easy 

 under the sledge ; or separate by means of the wedge, 

 or gad. It will stand battering by cannon balls, far 

 better than hard or flinty stone. It is the same with 

 timber. Hard wood will soon be shattered, broken, 

 riven and destroyed, by a batteiy of cannon: whereas 

 the palmetto^ and other such woods, being spongy and 

 soft, defy the attacks of the heaviest balls. Fort MouU 

 trie, in South Carolina, was during our revolutionary 

 war, an incontrovertible proof. Hard stone resists, and 

 is shocked and broken throughout. But the balls 

 make holes in their passage through soft stone, or wood, 

 very little larger than their diameters ; if they do not 

 bury themselves therein, which sometimes hapf^ens. 

 This fact can be ascertained ; and I have seen sundry 

 proofs of it. Some spongy wood will nearly again 

 close the perforation. 



If Anderson'' s ideas be correct, the soIidifyin,§' of mor* 

 tar depends on the coating and crystalHzacion of the 

 lime, on the surface, and in tb^ cavities, of every grain 

 ©f sand: which he says, is die better, the more it is sili^ 

 cious and rough ; and /lirnished with comers and protu^ 



berances, eucreasing the surface. He prefers rivef 



o o 



