INCIDENTAL EFFECTS OF HUMAN ACTION. 
541 
history. 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 in¬ 
stances, so far as yet examined, there are proofs that the coast 
has advanced 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 
respectively, 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 cast¬ 
away pottery of ancient towns in Magna Grsecia composes 
strata of such extent and thickness that they have been digni¬ 
fied with the appellation of the ceramic formation. The Rile, 
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 Rile by the wa¬ 
ter 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 house¬ 
hold refuse collected on the borders and within the limits of 
Cairo were so large, that the removal of them by Ibrahim 
Pacha has been looked upon as one of the great works of the 
age. 
The soil near cities, the street sweepings of which are 
spread upon the ground as manure, is perceptibly raised by 
