ii8 FAUM BUILDINGS. 6. 



weakening rather than flrengthening the ce- 

 ment. 



3. From the whole of thcfc experiments 

 it is evident, that the fevcral cements had ac- 

 quired the principal part of their fixed air j 

 chiefly, perhaps, after they were depofited in 

 the buildings. The air in the ftronger fpe- 

 cimens bears a confiderable proportion to the 

 entire quantity of cement ; and being infinu- 

 ated in theclofe flate above-mentioned, muft 

 have added greatly to its compaBnefs. 



Hence it is highlv probable , that the ftone- 

 like tenacity of old cements is chiefly ov/ing 

 to a tranfmutation fiom lime and land to cal- 

 careous earth and fand ;- — a fubflance rcfcm- 

 blino; the orip-inal limeftone. 



On examining a wall which has been built 

 with loam alone, without any admixture of 

 lime, and which ha? probably ftood about a 

 centurv, I find that the lo.im haS laid no hold 

 whatever of the ftoncs ; and that time has 

 made no alteration on its contexture. It is 

 flill the fame friable fubflance it prob.ibly 

 was the day it firll became dry in the build- 

 ing; without having the fmalleft appearance 

 of acquired tenacity, obtained during the 



century 



