Page:Great Neapolitan Earthquake of 1857.djvu/78

The fissures being widest at top, and becoming a scarce visible line at part of the way down the walls, or perhaps extending to their base, the earth wave, if in the direction ${\displaystyle a}$ to ${\displaystyle b}$, reaches the end wall, ${\displaystyle a}$, first. Its inertia acts as an equal and opposite force at its centre of gravity, and tends to cause it to be left behind while the remainder of the building is pushed forward. The end wall towards the direction from which the shock has come moves in the