shock nearly end on, remained in great part standing, and so saved all beyond them, while all lower down that part of the city was destroyed.
In part of a street in the humbler part of Pertosa, Photog. No. 67, (Coll. Roy. Soc.,) the shock was nearly in the perpendicular, to the plane of the picture, and from the observer. One side of the street, that on the right hand, is almost quite down; the opposite one was comparatively safe. The houses were much of the same character at both sides; but on one side the shock pulled out the fronts, that have fallen away from the roofs and joists, which had no hold upon them owing to the method of construction, while it pressed inwards, against the firmly resisting edges of the floors and roofs the other side, which the wave, in its return vibration, had not sufficient velocity in its horizontal component to bring down.
In Photog. No. 68, (Coll. Roy. Soc.,) some of the highest houses in Polla were left standing tolerably safe, though full of apertures, and arched galleries in front; while the same street, lower down and near the front of the picture, was choked with the ruins of houses, of only half the height or less. The former were new and well built in comparison with the latter.
If in place of the town standing upon pretty level ground, as previously assumed, it stand upon a hill summit, and on its flanks, the difference of devastation, at different sides, is usually great. If, as in Fig. 69, the shock emerge in the direction —, the buildings at the right and left, are differently affected, because their grasp upon the ground at their foundations is different, the relative direction of emergence different (as will be more fully examined when