the room, and (Fig. 200). Within a second or two after the chocolatière had begun to jump and make a noise,
the lithographs hanging upon the wall , began to oscillate slightly in the plane of the wall, or from east to west, and the reverse; and at the same instant, those hanging upon the wall , began to oscillate slightly, out from and back to that wall, i.e., in the same east to west direction. The great shock now arrived, and the frames upon the wall , at once began to sway forward and back in the plane of the wall, or in a direction south to north, and the reverse; while those upon the wall , commenced the movement out from and back to the wall; and for a moment or two he thought they all moved more or less both ways, viz., in the planes and at right angles to the planes, of both the east and west and north and south walls. The motion ended finally, by the prints on the wall , alone oscillating gently in its plane, with a decreasing motion, for two or three seconds, and finally coming to rest.
Of the lithographs upon the wall , the Sotto Intendente pointed out to me one, the dimensions of which (they were all quite similar) are given in Fig. 201, and he caused it to vibrate in both ways by his hand, as nearly as he could to the me extent, that he had observed it to have moved at the most violent period of the shock. The chord of the arc of vibration, in plane of the wall (east and west) was about 2 inches, and the semichord of the corresponding vibration, from and back to the wall , was about 1.25
