542 
EARTHQUAKES. 
them and by other effects of human industry, and in spite of 
all efforts to remove the waste, the level of the ground on 
wdiich large towns stand is constantly elevated. The present 
streets of Rome are twenty feet above those of the ancient 
city. The Appian way between Rome and Albano, when 
cleared out a few years ago, was found buried four or five feet 
deep, and the fields along the road were elevated nearly or 
quite as much. The floors of many churches in Italy, not 
more than six or seven centuries old, are now three or four feet 
below the adjacent streets, though it is proved by excavations 
that they were built as many feet above them. 
Resistance to Great Natural Forces. 
I have often spoken of the greater and more subtile natural 
forces, and especially of geological agencies, as powers beyond 
human guidance or resistance. This is no doubt at present 
true in the main, but man has shown that he is not altogether 
impotent to struggle with even these mighty servants of na¬ 
ture, and his unconscious as well as his deliberate action may 
in some cases have increased or diminished the intensity of their 
energies. It is a very ancient belief that earthquakes are more 
destructive in districts where the crust of the earth is solid and 
homogeneous, than where it is of a looser and more interrupt¬ 
ed structure. Aristotle, Pliny the elder, and Seneca believed 
that not only natural ravines and caves, but quarries, wells, 
and other human excavations, which break the continuity of 
the terrestrial strata and facilitate the escape of elastic vapors, 
have a sensible influence in diminishing the violence and pre¬ 
venting the propagation of the earth waves. In all countries 
subject to earthquakes this opinion is still maintained, and it 
is asserted that, both in ancient and in modern times, buildings 
protected by deep wells under or near them have suffered less 
from earthquakes than those the architects of which have neg 
lected this precaution.* 
* Landgp.ebe, Naturgeschichte der Vulkane , ii, pp. 19, 20. 
