Chap. IV. OF ANCIENT BUILDINGS. 191 



stones at Leith Hill Place and Stonehenge, 

 for the soil would have heen damp beneath 

 them. But the rate of sinking of the dif- 

 ferent parts would not have been quite equal, 

 and the floor was not quite level. The 

 foundations of the boundary walls lie, as 

 shown in the section, at a very small depth 

 beneath the surface ; they would therefore 

 have tended to subside at nearly the same 

 rate as the floor. But this would not have 

 occurred if the foundations had been deep, 

 as in the case of some other Roman ruins 

 presently to be described. 



Finally, we may infer that a large part of 

 the fine vegetable mould, which covered the 

 floor and the broken-down walls of this villa, 

 in some places to a thickness of 16 inches, 

 was brought up from below by worms. From 

 facts hereafter to be given there can be no 

 doubt that some of the finest earth thus 

 brought up will have been washed down the 

 sloping surface of the field during every heavy 

 shower of rain. If this had not occurred a 

 greater amount of mould would have accumu- 

 lated over the ruins than that now present. 

 But beside the castings of worms and some 



