sed
of many blocks, survive a shock which overturns lower buildings where
thin walls support several floors, on each of which is accumulated a
considerable amount of weight. In the case of the column, the strains
are even, and the whole structure may rock to and fro without toppling
over. As the energy of the undulations diminish, it gradually regains
the quiet state without damage. In the ordinary edifice the irregular
disposition of the weight does not permit the uniform movement which
may insure safety. Thus, if the city of Washington should ever be
violently shaken, the great obelisk, notwithstanding that it is five
hundred feet high, may survive a disturbance which would wreck the
lower and more massive edifices which lie about it.

Where, as is fortunately rarely the case, the great shock comes to
the earth in a vertical direction, the effect upon all movable objects
is in the highest measure disastrous. In such a case buildings are
crushed as if by the stroke of a giant's hand. The roofs and floors
are at one stroke thrown to the foundations, and all the parts of the
walls which are not supported by strong masonry continuous from top to
bottom are broken to pieces. In such cases it has been remarked that
the bodies of men are often thrown considerable distances. It is
asserted, indeed, that in the Riobamba shock they were cast upward to
the height of more than ninety feet. It is related that the solo
survivor of a congregation which had hastened at the outset of the
disturbance into a church was thrown by the greatest and most
destructive shock upward and through a window the base of which was at
the height of more than twenty feet from the ground.

It is readily understood that an earthquake shock may enter a building
in any direction between the vertical and the horizontal. As the
movement exhausts itself in passing from the place of its origin, the
horizontal shocks are usually of least energy. Those which are
accurately vertical are only experienced where the edifices are placed
immediately over the point where the motion originates. It follows,
therefore, that the destructive work of earthquakes is mainly
performed in that part of the field where the motion is, as regards
its direction, between the vertical and the horizontal--a position in
which the edifice is likely to receive at once the destructive effect
arising from the sharp upward thrust of the vertical movement and the
oscillating action of that w