167 



of the island of Manilla, contains within itself 

 great cavities, which are filled with atmosphe- 

 rical water, owing merely to filtration. The 

 aqueous vapours, which are exhaled by the nos- 

 trils and crevices of the crater, are only those 

 same waters heated by the interior surfaces dow n 

 which they flow. 



We had yet to scale the steepest part of the 

 mountain, the Piton, which forms the summit. 

 The slope of this small cone, covered with volca- 

 nic ashes, and fragments of pumice stone, is so 

 steep, that it would have been almost impossible 

 to reach the top, had we not ascended by an old 

 current of lava, the wrecks of which have resist- 

 ed the ravages of time. These wrecks form a 

 wall of scorious rocks, which stretches itself into 

 the midst of the loose ashes. We ascended the 

 Piton by grasping these half decomposed scoriae, 

 the sharp edges of which remained often in our 

 hands. We employed nearly half an hour to 

 scale a hill, the perpendicular height of which is 

 scarcely ninety toises. Vesuvius *, three times 



* According to the barometrical measurements, which Mr. 

 .Leopold von Buch, Mr. Gay-Lussac, and myself, took in 

 1805, the height of Vesuvius is diminished on the south-west 

 side since the year 1794, where a part of the cone fell in, two 

 days after the ashes had been ejected. Saussure found'Vesu- 

 vius, in 1773, 609 toises high, at a time when the brinks of 

 the whole of the crater were nearly of the same height. Sir 

 George Shuckburgh measured, in 1776 a hill placed in the 

 midst of the crater ; it was 615 toises in height. This hill 



i 



