Thickness., Cetnent and Materials of Walls. 207 



The i?omflfwwere attached to the system of thick walls, 

 formed in various modes. Some of them were faced with 

 lar^e stone, tied by headers, or binders, in proper pla- 

 ces; filled, in the middle, with pebbles or small stones; 

 and embodied by pouring in grout, or thin mortar. — 

 Much discussion has been had on the subject of their 

 masonry ; as well as on the nature and qualities of the 

 Roman cement. Lx)riot thought he had discovered the 

 mode of building; and the cement of the ancients. But 

 none succeed by pursuing his plans, or recipe, in large 

 works. He proposed erecting walls, between two 

 frames placed at the distances required, boarded up ; 

 tight, and capable of holding grout or cement of a cer- 

 tain composition. Pebbles and stones, of any shape, 

 or size, were to be thrown in these cases, at random. 

 The grout was to be poured in, from time to time 

 to fill the interstices : and the frames were to stand, till 

 the wall was dry and consolidated. In small baths, cis- 

 terns, and vats, something like his mode has succeeded 

 here. Not having seen his book for many years, I have 

 not a perfect recollection of his plan, or composition. 



It appeal's to be most probable, and it is now gene- 

 rally conceded, that the cement of the ancients, has ac- 

 quired its celebrity by the help of time; which has af- 

 forded the opportunity, through ages, to the lime, to at- 

 tract and recover ^^fxahle air; and thereby the mortar 

 has been again turned into stone. Time, in this case» 

 out of its usual course, strengthens ; and supplies the 

 deficiencies of human art. 



The mortar of the old Irish castles, built before the 

 tsra of Irish history, and dispersed through that king- 

 dom ; is as perfectly consolidated, as can be any Eoman, 



