constructed above the crossed arches of the nave, chancel, and transepts.
From the regularity of the structure, and its great size, I at once saw that the fissures presented data of the highest value, and devoted some hours to their exact drawing and admeasurements. When I had completed my work, one of the "Canonici" offered to bring me to Signor Guiseppe D'Errico, the architect of "the Chapter," from whom, he said, I could obtain much information. I found Signor D'Errico to be a gentleman of learning, great intelligence, and observation; he had already had accurate drawings made, to scale, of every fissure in the cathedral, with reference to the possibilities of reparation, and he obligingly offered me tracings of them. The Diagram No. 313 gives his figuring of the fissures in the vertical section along the axial line looking north, and also in horizontal section or plan. The fissures drawn in the latter, so far as the roof is concerned, are drawn as if looking up at them from the interior, those of the walls, &c., as if looking down on them. The vertical section and dome plan, are from the hand of Signor D'Errico, and bear his signature, drawn "dal vero;" and as he had no theoretic views whatever, as to any relation that might subsist between the directions, &c., of fissures, and that of the shock producing them, this drawing, which agreed with my own sketches and measurements, may be adduced as a valuable confirmation from a thoroughly competent and yet wholly unbiassed observer, of the correctness of the views advanced on this subject in Part I., as well as affording data of the most reliable kind. It will be needless to describe in detail those fissures and fractures which will be most perfectly understood by a careful
