Page:Great Neapolitan Earthquake of 1857.djvu/452

362 feet per second, which agrees very closely with previous determinations from other objects and at other stations.

The velocity thus obtained may be subject to two slight corrections, for which, however, the data are not obtainable. 1st. If the mortar at the old fracture of the base had any adhesion at all, (I believe it had none,) the velocity due to fracturing it, should be added.

2nd. The horizontal ordinate $$a$$ in the last equation is probably a little too great as measured, inasmuch as the fallen piece of the shaft must, by its own elasticity and that of the ground, have slid forward some fraction of an inch after it had struck the latter, which would make the velocity obtained a little too great.

These two errors, if they exist, tend to correct each other; and neither could affect the result to the extent of unity in the first decimal place. The result may therefore be relied upon.

In the same garden two vases of limestone, rudely hollowed out, had stood upon the opposite corners of the low parapet walls, that once confined the soil of beds, and separated them from broad walks between, now overgrown with dense turf and weeds, moss, twigs, &c.

These vases were both projected off their feet or lower portions, at a joint at $$e$$, Figs. 1 and 2, Diagram No. 222, and thrown to the ground, the lower portions remaining still upon the parapets, as seen in Photog. No. 220 (Coll. Roy. Soc.). One of the lower portions, ($$\mathrm{A}$$, Fig. 1,) I found square to the faces of the parapets, and obviously unmoved; the other, $$\mathrm{B}$$, had been twisted round 14°, so that two of its sides were in a line exactly north and south 14° W.

The lower portions at the joint $$e$$ (Figs. 1 and 3) were quite