time, were compared with the time at the Observatory, and one was found to have been slightly deranged by the railway journey. I had deemed it probable, that by the co-operation of some Neapolitan savant, I should be able to get measures of horizontal surface transit velocity of the earth-wave, in some of the slight shocks said to be still continuing. The uncertainty of their recurrence and difficulties as to finding any Neapolitan co-observer, rendered this impracticable. The chronometers were, however, of much service to me in the interior of the country, one of them having been adjusted to Naples mean solar time before I started.
The Salle Centrale has its length in the direction of the meridian. At one end a doorway, (Fig. 112) leads to a stone winding staircase, descending one deep story, and ascending to the equatorial, which is thus placed on the top of a cylindrical tower, formed of a central solid cylinder of masonry of about 6.5 feet diameter, the steps about 4 feet wide, and the outer cylindrical wall of about 3 feet in thickness; the total height from the ground to the floor of the equatorial being about 70 feet.
Fig. 113 is a section across the Salle Centrale at (Fig. 112), showing the interior elevation of the end next this tower. From the centre of the lintel of the doorway at , a nearly vertical fissure, open 0.20 inch at bottom, extends upwards, becoming evanescent at about twelve feet, and its plane is in that of the meridian. Its continuation downwards can be traced from the centre of the sill of the doorway also.
A second fissure at B, occurs right through the outer wall,
