EARTHQUAKES 255 
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the lateral vibration of earthquakes, but was disturbed by 
the vertical shocks and swayed badly in the wind. Milne 
mounted a room on a layer of cannon balls; it also rocked 
unpleasantly during high wind; but when the cannon balls 
were replaced by shot a quarter of an inch in diameter, the 
friction was enough to resist wind action, and the room re- 
mained at rest during earthquakes which caused violent 
oscillation in the adjacent ground. Milne concluded that the 
method is practicable for special purposes, but not for ordinary 
buildings. 
The defect of a free foundation is that though the oscil- 
lation is reduced in speed, the amplitude and actual move- 
ment may be increased. Weak beds generally form un- 
satisfactory foundations as their cavities collapse and loose 
patches become more closely packed. The insecurity of 
weak foundations can be overcome by tying all parts of the 
building together, so that it moves as a whole. The Temple 
of Diana at Ephesus is said to have been built on a marsh 
to protect it from earthquakes. It like other Greek temples 
was built on a massive platform that acted like a pontoon 
and protected the superstructure from waves in the founda- 
tion. This principle has been adopted by building regulations 
in earthquake areas; after the destruction of Casamicola 
in Ischia in 1883, it was enacted that each house must stand 
on a platform of masonry or cement 27 inches thick for a 
one-story and 47 inches for a two-story building. 
Loose foundations on steep slopes are dangerous, as earth- 
quakes there cause landslips; and the free vibration of the 
sides of a railway embankment may shake it into piles of 
sand. 
ErrecTs OF LATERAL MovEMENT—The lateral movement 
of the surface in an earthquake dismantles railways by jerk- 
ing the rails forward and buckling them into serpentine 
curves; bridges are broken by the girders riding forward, 
till one end falls off its pier. Bridges may also be destroyed 
by the vertical upward movement thrusting the piers through 
the roadway, which is dragged down by the descending 
movement ; this process is repeated and the roadway is 
transfixed by the piers. 
Buildings beside steep hill-sides and cliffs are often seriously 
damaged owing to the free movement on the hill-face. A