664 HENRY S. WASHINGTON 
the basalts; as I am with Bergeat’s conclusion as to the essential 
structural unity of Montagna Grande and Monte Gibelé, and his 
conclusion that the latter was the crater of the “andesite”? mass. 
My observations, however, lead me to different conclusions as to 
the presence of fault-lines and other lineaments, and the origin of 
the volcano of Monte Gibelé and Montagna Grande, the ring of 
scarps, and the Bagno dell’ Acqua. 
The straightness-and parallelism of the supposed fault-lines of 
Foerstner and Bergeat appear to me, after examination of the island 
and study of the large-scale chart, to be unduly emphasized. Asa 
matter of fact, the inner scarp and ridge of Serra di Ghirlanda with 
its orogenic continuation in the Cuddioli dietro Isola is far from 
being a straight line, curving gently round from a north-north- 
westerly direction at the north end, through north-south, to 
northeast-southwest at the southern end. A similar curvature is 
shown by the Costa Zichidi ridge, and also at that of Costa di 
Zeneti, which latter turns sharply, but without any tectonic 
discontinuity, into the ridge and scarp of Cuddia Nera, with an 
east-west direction. The scarp of the summit of Montagna 
Grande, on the other hand, while in general following the lines of 
the Ghirlanda—Zichidi ridges and facing them, shows essentially 
straight lines: one on the east with a nearly north-south direction 
and the other east-west, the two meeting in a sharp angle at the 
southeast corner of the mountain, at the Rione Miliac. On the 
west, northwest, and north, however, the mass of Montagna 
Grande shows no scarps which correspond to those of Costa Zeneti 
and Cuddia Nera. Furthermore, the eastern slopes of Monte 
Gibelé slope gently down, with typical volcanic cone topography, 
to the Piano di Ghirlanda, whereas if the Ghirlanda scarp was due 
to faulting, and if Monte Gibelé is an originally integral part of the 
Montagna Grande mass, as there is good petrographic and orogenic 
reason to believe, we should expect Gibelé also to show fault scarps 
marking the line of separation from the surrounding region. 
Again, it is difficult to conceive of the origin of the deep and 
narrow valleys surrounding Montagna Grande on the basis of 
either the fault or the upthrust theory. The one would explain 
them by the slipping down or differential movement of narrow 
