Page:Great Neapolitan Earthquake of 1857.djvu/427

Rh upon, but yet enough to convey a distinct notion of the extent of movement of a powerful earthquake shock.

The actual lateral movement here was probably about 3$1⁄2$ to 4 inches—a range of motion which, made with a velocity as great, as that with which one reaches the ground, on leaping down from a height of 2$1⁄2$ feet, may enable one easily to understand how readily persons are thrown down when exposed to it.

The Secretary Lansalone pointed out to me in his house two brass table lamps, fashioned as in Fig. 203, which stood upon a semicircular table, placed with its diametral side, in contact with a wall running 37° W. of north, the lamps being placed so that the line $$x y$$ was at right angles to the plane of the wall. The centre of gravity of either lamp, is 7 inches above the base, and the centre of oscillation is about 10 inches above the edge of the base, considered as centre of motion. The weight by trial = 1 rotulo 2 unci.

At the shock one of these lamps was thrown off the table towards the north and the other towards the south, and lay upon the floor in the positions shown in Photog. No. 205, (Coll. Roy. Soc.), and Fig. 204. The china things upon the same table remained as seen by me, nearly undisturbed: they were low and broad based.

The legs of the table were somewhat elastic, and as they sprung under the shove from the wall, in contact with it, no deduction as to wave velocity can be made from these lamps. Making some allowance for the effects of this elasticity, in giving divergence to the direction of throw,