FIG. 101. RUINS AT POZZUOLI, ITALY 



Study of these ruins has shown that: 1. The deposit of several feet 

 of sediment upon the floor caused the building to be abandoned. 2. Later 

 a second floor was laid upon the sediment, indicating that the building was 

 used again. 3. Several feet of deposit were removed 200 years ago, re- 

 vealing the remains of shells grown upon the pillars. What change of 

 level is indicated (a) by the covering of the first floor? (6) by the laying of 

 the second? (c) by the presence of shells? 



