272 Natural History of Volcanos and Earthquakes. 



consisting of two peaks, which they probably would have done, 

 if the Monte Sonima had stood, as at present, distinct from the 

 cone of Vesuvius.* It is also remarked that the distance men- 

 tioned in ancient writers, as intervening between the foot of 

 Vesuvius and the towns of Pompeii and Stahiae^ appears to 

 have been greater than exists at present, unless we measure it 

 from the foot of Monte Somma, so that this affords an additional 

 probability, that the latter mountain was then viewed as a part 

 of the former, and that no separation between them had at that 

 time occurred. We may also be sure from the semicircular fig- 

 ure which the southern escarpment of the Monte Somma pre- 

 sents towards Vesuvius, that it constituted a portion of the walls 

 of the original crater ; and Visconti, it is said, has proved by ac- 

 tual measurements, that the centre of the circle, of which it is a 

 segment, coincides as nearly as possible with that of the present 

 crater. There seems, therefore, little room to doubt, that the old 

 mouth of the volcano occupied the spot now known by the name 

 of the Attrio del Cavallo, but that it was greatly more extensive 

 than this hollow, as it comprehended likewise the space now 

 covered by the cone, which was thrown up afterwards in con- 

 sequence of the renewal of the volcanic action that had been 

 suspended during so many ages. This view likewise tends, as 

 it seems, to reconcile the accounts which ancient writers have 

 given of the structure of the mountain, antecedently to the pe- 

 riod before mentioned.! 



As for the mode of action of the vapors, it is indifferent whether 

 they have to contend with loose and unconnected, or with melt- 

 ing masses, only that the former are propelled into the air like 

 cannon balls,| and falling into a parabolic curve, accumulate and 



* Daubeny, a Description of Active and Extinct Volcanos, &c. p. 144. See 

 also Von Buch in PoggendorfF's Ann. t. xxxvii, p. 173. 



t See the Historical Notices given by Daubeny, loco cit. p. 145, and following. 



+ V. Humb. (Reise, v. i, p. 226) calculates from the time the stones thrown out 

 during the lateral eruption of the Peak of Teneriffe, on the 9th June 1798, took 

 in falling (which according to Cologan was from twelve to fifteen seconds, reck- 

 oning from the moment they reached their greatest height,) that they were pro- 

 jected to a height of more than 3000 feet. In some similar observations made by 

 Von Humboldt during the eruptions of Vesuvius in 1805, he satisfied himself that 

 such observations are capable of a great degree of exactitude. Similar calcula- 

 tions made by other observers, give still greater heights. The maximum height 

 of such projections was observed at Cotopaxi by La Condamine (Voyage a I'Equa- 

 teur.) He saw propelled laterally, a block of about 1000 square feet, to a distance 

 of nearly 1^ geographical miles. 



