CHAP. TV OF ANCIENT BUILDINGS. 219 



than the other half without any assignable 

 cause. In a bricked passage to Mr. Joyce's 

 own house, laid down only about six years 

 ago, the same kind of sinking has occurred as 

 in the ancient buildings. Nevertheless it does 

 not appear probable that the whole .amount 

 of sinking can be thus accounted for. The 

 Roman builders excavated the ground to an 

 unusual depth for the foundations of their 

 walls, which were thick and solid ; it is 

 therefore hardly credible that they should 

 have been careless about the solidity of the 

 bed on which their tesselated and often 

 ornamented pavements were laid. The sink- 

 ing must, as it appears to me, be attributed 

 in chief part to the pavement having been 

 undermined by worms, which we know are 

 still at work. Even Mr. Joyce at last ad- 

 mitted that this could not have failed to have 

 produced a considerable effect. Thus also the 

 large quantity of fine mould overlying the 

 pavements can be accounted for, the presence 

 of which would otherwise be inexplicable. My 

 sons noticed that in one room in which the 

 pavement had sagged very little, there was an 

 unusually small amount of overlying mould. 



