14 



J. W. Judd — On Volcanos. 



to the formation in them of beautiful veins of selenite, accompanied 

 by Misy and other basic sulphates of iron, which are found inter- 

 secting them in all directions. As an illustration of one among the 

 many difficulties, the like of which we may not unnaturally anticipate 

 experiencing, when seeking to define the exact character of some 

 volcanic products of former geological periods, I may mention that, 

 in some cases the bands of finer-grained ash in Lipari are converted 

 into an intensely hard rock of jaspery aspect, and with a conchoidal 

 fracture, to which — but for its mode of occurrence, its gradation into 

 the ordinary tuffs around, and the plant-remains which it not tinfre- 

 quently contains — probably no geologist would dream of attributing 

 its true mode of origin. 



Of the lavas and tuffs of the second period of volcanic action in 

 the Lipari Islands, a number of volcanic cones are built up, the 

 craters of which, though usually clearly traceable, are often in the last 

 stage of ruin and decay. Of these cones and craters we may instance 

 the islands of Alicudi and Filicudi, each of which is a volcanic 

 mountain rising directly out of the sea to the heights of 2,172 and 

 2,598 feet respectively, with vestiges of craters at their summits ; 

 in Salina we have the two similarly ruined volcanos of Monte Porri 

 (2,850 feet) and Monte Salvatori (3,125 feet), the highest summit 

 in the Lipari Islands ; in the island of Lipari the lavas and tuffs we 

 are now describing compose the Monte Sant' Angelo, the culminating 

 point of the island, with its great axial crater and several smaller 

 lateral ones on its eastern and western flanks; in Vulcano the period 

 is represented by the series of ruined craters, forming all the southern 

 parts of the island, and culminating in Monte Sarraceno (1,601 feet) : 

 and, lastly, the central cone of Stromboli, having an elevation of 

 3,090 feet, with the doubtful crater at its apex, and the much clearer 

 one on its southern flank, also belongs to the same period. 



In examining these old and much denuded craters, of which that 

 on Monte Sant' Angelo (represented in Fig. 3) affords an excellent 



Fig. 3. — Ruined Crater of Monte Sant' Angelo in Lipari, as seen from the summit of the 

 Monte d-ella Guardia in the same island. 



example, the stratified arrangement of the tuffs, with converging 

 dips in their interior parts and diverging ones exteriorly, a feature 

 so characteristic of the structure of all volcanic cones (see Scrope's 

 'Volcanos,' 2nd ed. p. 60), is often very admirably displayed. The 

 lava-streams can often be traced to their points of issue from the 



