662 HENRY S. WASHINGTON 
insignificant beds of travertine and the lacustrine deposits of the 
Rione di Bagno, the rocks are wholly volcanic. Some fragments of 
granite found by Foerstner™ and Soellner? in several places on the 
island indicate that the foundation is of this material. I was not 
fortunate enough to meet with any of these, but observed fragments 
of diorite in the lava of the island of Linosa,3 so that a basement of 
plutonic rocks may be inferred for the bed of this part of the 
Mediterranean. 
Of the earlier view as to the structure, only mention may be 
made that Pantelleria was cited as an illustration of von Buch’s 
theory of craters of elevation, the circle of scarps surrounding 
Montagna Grande being supposed to be due to elevation incident 
to the formation of this volcano. 
Foerstner’s views.—F oerstner has discussed the geological struc- 
ture at some length. In the following summary his rock-names 
will be retained. According to Foerstner the first eruptions on the 
granite base were of “‘phonolite” and “‘liparite,’’ which uniformly 
underlie the other lavas, and which issued from a now vanished vent. 
These were covered by the “andesites” of Monte Gibelé, which 
was also probably the volcanic center of the lavas of Montagna 
Grande, then not raised to its present height. From an unknown 
center of the same epoch are supposed to have issued the “‘ande- 
sites”? which form the surface of Costa Zichidi, and which are prob- 
ably the latest flows of this stage. The next period was that of the 
eruption of the first pantellerites, especially of the crystalline 
variety, which poured out of numerous vents all around the large 
andesitic volcano. The Bagno dell’ Acqua is supposed to belong to 
this period and to have been an explosion crater, while the Cuddia 
Attalora is a well-preserved parasitic cone of the same period. - 
The ejection of this mass of lava caused profound dislocations 
and resulted in the upthrust of the mass of Montagna Grande, 
which was accompanied by the formation of many subsidiary cones 
on its flanks and the pouring-out of flows of vitreous pantellerite, as 
‘HH. Foerstner, Boll. Com. Geol. Ttal., 1881, p. 550. 
2 J. Soellner, Zeits. Kryst., XLVI (1909), 522. 
3H. S. Washington, Jour. Geol., XVI (1908), 6. 
4H. Foerstner, Boll. Com. Geol. Ital., 1881, pp. 550-53. 
