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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 23, 



from the apex downwards (fig. 2, c). The dotted hnes in fig. 2 

 (after Hamilton) represent the shape of the outer and inner cones 

 before this eruption, and the space between them and the firm out- 

 line represents the amount by which the cone was in the intervening 



Fig. 2. — Outline-sketch of Vesuvius as it appeared in October 17^7 ; 

 with dotted outlines of its form in July and in May of the same 

 year. 



ten years augmented in bulk and height by the ejectamenta of that 

 eruption. An interval of comparative tranquillity followed, until, in 

 1 794, the paroxysmal eruption occurred, described by Breislak, which 

 completely gutted this cone, then solid, lowered its height, and left 

 a crater of great size bored through its axis. Later eruptions, espe- 

 cially that of 1813, not merely filled up this vast cavity with their 

 products, but once more raised the height of the cone by some hun- 

 dred feet. When I first saw it in 1819 the top formed a rudely 

 convex platform, rising towards the south, where was its highest 

 point. Several small cones and craters of eruption were in quiet 

 activity upon this plain, and streams of lava trickled from them 

 down the outer slopes of the cone. So things went on until October 

 1822, when the entire heart of the cone was again thrown out by the 

 formidable explosions I have so often referred to, and a vast crater 

 was opened through it ; while the cone itself was found to have lost 

 several hundred feet from its top. In fact, nothing but an outer 

 shell of it was left (fig. 3). Eruptions, however, soon recommenced. 

 In 1826-7 a small cone was formed at the bottom of the crater, and, 

 continuing in activity, had reached a height which rendered it visible 

 from Naples in 1829, when of course it must have nearly filled up 

 the crater. In 1830 it was 200 feet higher than the crater's rim ; 

 and in 1 83 1 this cavity was completely filled, and the lava-streams 

 began to flow over it down the outer cone. In the winter of that 

 year a violent eruption once more emptied the bowels of the moun- 

 tain, and left a new crater, which soon began to fill again from ejec- 

 tions upon its floor; and by the month of August 1834 this crater 

 had been in its turn obliterated, and lava overflowed its edge towards 

 Ottaiano. In 1839 the cone was again cleared out, and a new crater 



