CHAP. IV. OF ANCIENT BUILDINGS. 231 



ing surface and thus afforded some shelter. 

 The floors of the old rooms, halls and passages 

 have generally sunk, partly from the settling 

 of the ground, but chiefly from having been 

 undermined by worms; and the sinking has 

 commonly been greater in the middle than 

 near the walls. The walls themselves, when- 

 ever their foundations do not lie at a great 

 depth, have been penetrated and undermined 

 by worms, and have consequently subsided. 

 The unequal subsidence thus caused, probably 

 explains the great cracks which may be seen 

 in many ancient walls, as well as their 

 inclination from the perpendicular. 



