Abstract

In the year 1864 I was enabled to employ some time in the study of some of the chief volcanic phenomena presented by the cone of Etna, devoting my attention principally to the laws which govern the flow of lava currents, the formation of the parasitic cones which abound upon certain portions of the surface of the great mountain, of which Monte Rosso and Monte Peleri in the neighbourhood of Nicolosi are amongst the largest examples, and in examining the Val del Bove and the many so-called dykes which intersect its surrounding escarpment in so many places. These last objects were examined by me with the able memoir of Sir Charles Lyell, published in the Philosophical Transaction for 1858, in hand, the title of which is “on Lavas of Mount Etna,” &c.

In the second part of that memoir the author rests part of the evidence upon which he concludes that an ancient great vent existed in the Val del Bove at Trifoglietto, upon the convergence at about that point of the prolonged lines of direction of thirteen dykes existing in the surrounding escarpment, in accordance with the views previously promulgated by Von Waltershausen (Phil. Trans., Part ii. 1858, page 703). I have no intention of casting any doubt here upon any part of the above able memoir of Sir Charles Lyell, in all the main conclusions of which, indeed, I concur, my present object being limited to remarking upon some of the conditions which affect the formation of volcanic