INCIDENTAL EFFECTS OF HUMAN ACTION. 641 
Wherever the coast line appears, from other evidence, to have 
remained unchanged in outline and elevation since they were 
accumulated, they are found near the sea, and not more than 
about ten feet above its level. In some cases they are at a 
considerable distance from the beach, and in these instances, 
so far as yet examined, there are proofs that the coast has ad- 
vanced in consequence of upheaval or of fluviatile or marine 
deposit. Where they are altogether wanting, the coast seems 
to have sunk or been washed away by the sea. The constancy 
of these observations justifies geologists in arguing, where 
other evidence is wanting, the advance of land or sea respect- 
ively, or the elevation or depression of the former, from the 
position or the absence of these heaps alone. 
Every traveller in Italy is familiar with Monte Testaccio, the 
mountain of potsherds, at Rome ;* but this deposit, large as it 
is, shrinks into insignificance when compared with masses of 
similar origin in the neighborhood of older cities. The castaway 
pottery of ancient towns in Magna Greecia composes strata of 
such extent and thickness that they have been dignified with 
the appellation of the ceramic formation. The Nile, as it 
slowly changes its bed, exposes in its banks masses of the same 
material, so vast that the population of the world during the 
whole historical period would seem to have chosen this valley as 
a general deposit for its broken vessels. 
The fertility imparted to the banks of the Nile by the 
water and the slime of the inundations, is such that manures 
are little employed. Hence much domestic waste, which 
would elsewhere be employed to enrich the soil, is thrown out 
into vacant places near the town. Hills of rubbish are thus 
piled up which astonish the traveller almost as much as the 
solid pyramids themselves. The heaps of ashes and other 
* Until recently this hillock was supposed to consist of sherds of household 
pottery broken in using, but it now appears to be ascertained that it is com- 
posed of fragments of earthenware broken in transportation from the place 
of manufacture to the emporium on the Tiber where such articles were 
landed, 
41 
